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An assessment of survey measures used across key epidemiologic studies of United States Gulf War I Era Veterans

Environmental Health volume 12, Article number: 4 (2013) | Download Citation

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Abstract

Over the past two decades, 12 large epidemiologic studies and 2 registries have focused on U.S. veterans of the 1990–1991 Gulf War Era. We conducted a review of these studies’ research tools to identify existing gaps and overlaps of efforts to date, and to advance development of the next generation of Gulf War Era survey tools. Overall, we found that many of the studies used similar instruments. Questions regarding exposures were more similar across studies than other domains, while neurocognitive and psychological tools were the most variable. Many studies focused on self-reported survey results, with a range of validation practices. However, physical exams, biomedical assessments, and specimen storage were not common. This review suggests that while research may be able to pool data from past surveys, future surveys need to consider how their design can yield data comparable with previous surveys. Additionally, data that incorporate recent technologies in specimen and genetic analyses would greatly enhance such survey data. When combined with existing data on deployment-related exposures and post-deployment health conditions, longitudinal follow-up of existing studies within this collaborative framework could represent an important step toward improving the health of veterans.

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Background

Approximately 697,000 members of the U.S. Armed Forces were deployed to Southwest Asia in support of the 1990–1991 Gulf War. More than 4 million remaining troops were deployed elsewhere or not deployed. Elevated rates of measurable symptomatology and illness in Gulf War Era veterans have been well documented [1–4], with the excess burden of symptom prevalence estimated to be as high as 25-30% among deployed Gulf War troops, while their disease-related mortality remains equivalent to, or even lower than, that of the general population [1–6]. Many epidemiologic studies have been performed to understand the physical and psychological symptoms observed in and reported by veterans who served during this conflict era [1, 2, 4, 7–17]. However, a clear pathologic explanation or overarching diagnosis has remained elusive. While studies initially focused on post-deployment mental health, the number of reports of medically unexplained chronic multisymptom illness in this veteran population increased during the 1990s [18, 19]. This attracted the attention of researchers in several disciplines, including immunology, toxicology, neurology, occupational (military) health, epidemiology, and environmental health. Consequently, assessments in research expanded to address physical health, symptoms, and deployment-related exposures. Relative to epidemiological research in most other clinical areas, Gulf War-related studies have involved a wide diversity of outcome measures, risk factors, cohort characteristics, and methods. Novel strategies will be required to unify and harmonize the approach to both clinical care and research for this population in the setting of such broad clinical outcomes and diverse risk factors.

A deeper understanding of the tools used by past studies will enable critical evaluation and direction for future efforts. The Institute of Medicine and the Research Advisory Committee on Gulf War Veterans’ Illnesses have both completed comprehensive reviews of Gulf War research [20–23]. However, these focused primarily on the findings of the many studies conducted thus far, and not the research tools used to gather the studies’ data. There has not been a recent systematic review of the broad range of assessments used in Gulf War research. In this manuscript, we describe and review the research tools used by the fourteen major Gulf War Era studies to date. It is our intent that this information will assist ongoing research efforts through the following two focused purposes: to provide an overview of the assessment tools used in past studies, and to discuss how future Gulf War research may benefit from consideration of commonalities and gaps in the epidemiologic research.

Inclusion and exclusion criteria

We used three primary criteria to select candidate studies for inclusion in this review. First, we included epidemiologic studies of U.S. veterans that were considered “major cohorts” by the Institute of Medicine’s (IOM) 2009 Gulf War and Health review [22], according to their specified criteria for methodologic rigor, health outcomes assessment, medical evaluations, and use of laboratory testing. Second, we included two Gulf War veteran registries established by the Departments of Veterans Affairs and Defense; while these necessarily suffer from the limitations common to registries, such as non-generalizability and absence of a control group, they jointly comprise a vast repository of standardized data that may be useful in future carefully constructed research efforts. Finally, we considered studies reported since the IOM’s 2009 review, and ongoing studies.

We excluded studies of non-U.S. veterans and clinical studies or trials related to specific disease entities. Substudies of primary studies were included under the umbrella of their original study.

These criteria resulted in a total of twelve epidemiologic studies and two large government registries. The specific studies are: Devens Cohort Study (Devens, originally the Ft. Devens Operation Desert Storm Reunion Survey) [7, 24], New Orleans study [8], National Survey of Gulf War Era Veterans and Their Families (National Health Survey) [10], Pennsylvania-Hawaii study [17], Iowa study [2], Air National Guard study [4], Navy Seabees study [12], Oregon-Washington study [13], cross-sectional Kansas study (Kansas I) [1], case–control Kansas study (Kansas II) [14], Millennium Cohort Study [15], Military Health Survey [16], and the VA Persian Gulf War Health Examination Registry (VA Registry) [9] and DoD Comprehensive Clinical Evaluation Program Registry (DoD Registry) [11]. A tabulation of study characteristics is contained in Table 1. Demographic characteristics of the study participants are summarized in Table 2.

Table 1 Design characteristics of major studies of U.S. veterans of the first Gulf War
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Table 2 Characteristics of participants in major studies of U.S. veterans of the first Gulf War a
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Survey instruments

The major domains surveyed by the studies and registries are summarized in Tables 3, 4, and 5. These comprise the domains of mental and physical health (Tables 3 and 4) and deployment-related exposures (Table 5). These areas are commonly assessed during epidemiological research on military cohorts.

Table 3 Health domains surveyed by major studies of U.S. veterans of the first Gulf War
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Table 4 Psychological status evaluations used in major studies of U.S. veterans of the first Gulf War
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Table 5 Deployment-related exposure domains surveyed by major studies of U.S. veterans of the first Gulf War
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As described in further detail below, the domains of mental and physical health include health status, functional status, symptoms, fatigue complex (fatigue, chronic fatigue syndrome (CFS), fibromyalgia, and multiple chemical sensitivities), post-traumatic stress disorder (PTSD), neurocognitive and/or psychological status, and clinical evaluations and validations. The domains of environmental exposures include vaccinations, medications, airborne exposures, radiation sources, sources of infection or contaminants, psychological trauma, and behavioral risk factors. Each of these exposure domains has multiple subdomains. This review is not a comprehensive representation of all areas of research in these studies, but includes the domains most frequently studied thus far, that are arguably perceived to be the most critical.

Mental and physical health domains

Medical history and clinical diagnoses

Comparable survey measures were used by multiple studies. Eight studies (Devens, Kansas I, Kansas II, National Health Survey, Millennium Cohort, Seabees, Military Health Study, and a VA Registry sub-study) asked whether participants had been diagnosed or treated by a clinician for any of several medical conditions. There was substantial overlap in the conditions queried, including diabetes, depression, asthma, bronchitis, and chronic fatigue syndrome [1, 9, 12, 14, 24, 25, 29, 34, 35, 146]. It was also common to ask the approximate onset date for each condition. In contrast, Oregon-Washington and the VA and DoD registries had open-ended questions about health history, which resulted in a broad range of responses that are not easily comparable [9, 30, 48, 62].

Some instruments were used by only one study. For example, Iowa alone drew questions from instruments such as the National Health Interview Survey [147], the Behavioral Risk Factor Surveillance Survey [148], and the Agricultural Health Study [2, 149, 150].

Symptoms

Symptoms were assessed by all of the studies. They were typically queried by asking if the veteran had experienced persistent or recurring symptoms during the 12 months prior to the survey, using a symptom checklist. The number of symptoms surveyed varied by study (8 to 78 symptoms). In addition, some studies collected information about symptom severity and date of onset [1, 3, 4, 10, 12, 14, 16, 17, 24, 29, 30, 34, 35, 48, 60, 62, 136, 151–153]. New Orleans [8] and Devens [25] evaluated symptoms using the Health Symptom Checklist [81, 82]. Devens also used a variant of the Psychosomatic Complaint Scale (Psychological Well-Being Scale) [26, 79, 154, 155]. In later survey versions, Devens used the Expanded Health Symptom Checklist, which included additional questions on symptom presence during the past 30 days, duration, trajectory, and frequency [3, 25, 26]. National Health Survey used the 15-item Patient Health Questionnaire to measure the occurrence of somatic symptoms during the 4 weeks prior to survey administration [29, 156].

In this subdomain, the registries and Iowa differed the most from the rest of the studies. The registries both used open-ended questions to assess symptoms, instead of a binary format [9, 30, 48]. Iowa asked additional questions about symptoms of asthma and bronchitis from the American Thoracic Society Questionnaire [157, 158].

Functional status and health status

Of the eight studies that evaluated functional status, all used the SF-12, SF-36, or Veterans SF-36, either alone or in combination [2–4, 16, 29, 34, 39, 53, 63, 159–163]. The only study that asked questions to further evaluate functional status was the Iowa study, which administered the Health Utilities Index-Mark 3 [164, 165].

Health status was one of the most commonly assessed domains. All of the studies, with the exception of Pennsylvania-Hawaii, administered a health status evaluation. However, few of the instruments were directly comparable because their response scales varied, making it difficult to compare the responses. For instance, the Military Health, National Health Survey, Air National Guard, Kansas II, VA Registry, and Seabees all asked a general health rating question [4, 9, 12, 14, 24, 29, 35, 48, 153]. However, National Health Survey, Air National Guard, and the VA Registry used a five-category response scale, while Kansas II used a four-category response scale, and the Seabees used a three-category response scale. In addition, the response scale anchor points used by Air National Guard and National Health Survey differed from that used by the VA Registry, and the responses cannot be directly compared.

Chronic multisymptom illness and related diagnoses

It is estimated that chronic multisymptom illness and other symptom-based diagnoses affect up to 25 to 32% of the Gulf War veteran population [23]. Although several instruments have been developed to diagnose these conditions, they are still challenging to distinguish due to the number of their symptoms that overlap with other illnesses. Eleven of the studies collected data on at least one of these illnesses: fatigue, chronic fatigue syndrome, fibromyalgia, multiple chemical sensitivity, and multi-symptom illness.

Fatigue was assessed by Iowa, Devens, and a VA Registry substudy using the Chalder Fatigue Scale [2, 60, 166], the Fatigue Severity Scale [40, 167], and the Multidimensional Fatigue Inventory [49, 168], respectively. Chronic fatigue syndrome was most commonly identified in National Health Survey, Iowa, VA Registry, Air National Guard, Kansas II, Military Health Study, a Devens substudy, and Seabees [2, 4, 12, 14, 24, 29, 31, 35, 41, 53, 169] using the Centers for Disease Control definition developed by Fukuda [169]. In addition, a National Health Survey substudy validated self-reported chronic fatigue syndrome, fibromyalgia, and other conditions by physician examination [53]. Fibromyalgia was evaluated by four studies (Iowa, a National Health Survey substudy, Military Health Study, and Oregon-Washington) using the American College of Rheumatology criteria [2, 35, 53, 62, 170, 171]. Multiple chemical sensitivity was queried in five studies, but they each used different measures. These measures included the Chemical Odor Intolerance Index and a scale developed by the Agency for Toxic Substances and Disease Registry [35, 49, 50, 172, 173] and multiple internally-developed measures [12, 25, 40, 41, 174]. Several studies inferred the presence of medically unexplained multisymptom illness based on the symptoms and medical conditions that they surveyed [1, 4, 12, 14, 17, 24, 35, 41, 175, 176]; however, the 2005 National Health Survey asked questions specifically about participants’ experiences with unexplained multisymptom illness. These included years of first and most recent experience, activities and treatments that improve or aggravate the condition, and status relative to initial diagnosis [29, 153]. In addition to questions about chronic fatigue syndrome, fibromyalgia, and multiple chemical sensitivity, the Military Health Study contained a large number of self-constructed questions about illness symptoms in support of their goal of validating a case definition for Gulf War Illness [16, 35].

Post-traumatic stress disorder (PTSD)

Combat-related stress was initially hypothesized to be one of the factors responsible for the illnesses afflicting Gulf War veterans [177]; as a result, it was one of the few factors surveyed by all of the studies. The most frequently used instruments included the Clinician Administered PTSD Scale (4 studies) [30, 42, 48, 54, 178, 179], PTSD Checklist Military and Civilian versions (6 studies) [2, 8, 25, 26, 29, 40, 60, 63, 64, 180, 181], Mississippi Scale for Combat-Related PTSD (3 studies) [61, 63, 182], Mississippi Scale for Desert Storm War Zone Personnel (3 studies) [4, 8, 42, 183], the Structured Clinical Interview for DSM-III-R - Patient Edition (3 studies) [30, 44, 48, 90, 184], and the Impact of Events Scale (2 studies) [51, 58, 185]. Additional PTSD instruments, including the Penn Inventory for PTSD, were used by individual studies [63].

Psychological status

Psychological status is a very broad subdomain and is by far one of the most discordant areas in assessment across studies. It includes several fields, such as family and social support, intelligence, personality, psychiatric status, depression, anxiety, memory, executive function, psychomotor function, health perception, and quality of life. There were a total of 59 tests used in this domain, and all of the studies except Kansas I and Kansas II evaluated at least some of the fields. Many of the survey instruments and tests were only used by one study, but the most frequently used instruments were the Wechsler Adult Intelligence Scale and the Trail-Making Tests, which were each used by 5 studies to measure intelligence and executive function, respectively. A summary of the instruments used to evaluate psychological status can be found in Table 4.

Clinical evaluations and stored biospecimens

Several of the studies have performed detailed clinical evaluations, including complete physicals with standard laboratory tests (VA and DoD Registries, Iowa, Air National Guard, Oregon-Washington, and a National Health Survey substudy) [4, 9, 13, 24, 30, 53, 165]. Both registries have implemented a battery of additional laboratory tests for veterans requiring further evaluation [9, 30, 52]. The Devens and Military Health studies have performed MRIs [16, 35, 43]. Many of the studies have performed analyses using blood specimens, particularly for clinical laboratory measures; however, for most, it is not clear whether sufficient samples remain to support additional biomarker research. To our knowledge, only Seabees, Military Health Study, and Kansas II have collected biospecimens for future studies [14, 16, 31, 35, 186].

Healthcare expenditures and utilization

Veterans of this era varied in their approaches to utilizing healthcare services, and this variability was noted both within and between deployed and non-deployed veterans. In particular, participation in health registries that involved a clinical evaluation, such as the VA and DOD registries, accounted for a significant number of medical encounters. Health expenditures were directly addressed only by Iowa, using the National Health Interview Survey and the National Medical Expenditure Survey [2, 187–189]. Iowa also administered a telephone survey on health utilization to a subsample of their population who suffered from multiple chemical sensitivity [190]. Devens and National Health Survey used rough measures of health utilization, asking the number of clinic visits or hospitalizations [10, 26].

Deployment-related exposure domains

Vaccinations

Receipt of vaccinations prior to or during deployment was assessed by all but two studies (New Orleans and Pennsylvania-Hawaii). The vaccinations queried included anthrax, botulinum, typhoid, meningococcus, plague, a generic “any vaccinations,” and receipt of immune globulin. The form and scope of the questions can be divided roughly into two categories: those that asked whether any vaccines had been received (Iowa, Kansas I, Kansas II, Air National Guard, and Military Health Study) [1, 2, 14, 33, 35], and those that asked if specific vaccines had been received (Devens, VA and DoD Registries, National Health Survey, Seabees, Oregon-Washington, Millennium Cohort, and Military Health Study) [10, 12, 15, 25, 30, 32, 35, 40, 48, 51, 136].

Medications

Three medications were commonly assessed: malaria prophylaxis (any), ciprofloxacin and/or other antibiotics, and pyridostigmine bromide [2, 3, 10, 12–14, 31, 35, 48, 51, 134, 138, 142]. Use of these medications was queried using a binary format, or a categorical format that could be collapsed to binary. However, it was common to attempt to elicit additional details of pyridostigmine bromide use, in the form of the total number of pills used, frequency of use, number of days on which a certain dose was exceeded, and the occurrence of specified side effects or feelings of illness after using the pills [2, 13, 35, 51, 134, 136]. Some studies also asked open-ended questions about the use of over-the-counter and prescription medications [13, 35].

Airborne exposures

Many of the Gulf War studies assessed exposure to airborne toxins. These contaminants included petroleum fuels, solvents, fumes, smoke, combustion products from oil fires or incinerated trash/feces, tent heater smoke, vehicle exhaust, chemical agent resistant compound paint, debris from missile or artillery explosions, and chemical or biological warfare agents.

All of the studies except Kansas I asked questions regarding airborne exposures. These exposures were most commonly assessed using a binary response or a categorical format that could be collapsed to binary. In addition, several studies asked additional questions about the number of days or times exposed to airborne toxins; these types of questions had either open-ended or categorical response types [3, 10, 12–14, 17, 25–27, 31, 35, 38, 48, 51, 58, 136, 138, 142, 143]. In addition, Iowa asked whether the exposure was temporally associated with feelings of illness [38].

Radiation sources

The most commonly surveyed sources of radiation were depleted uranium and microwaves. Most of the studies queried these exposures using a binary or a categorical format that could be collapsed to binary [10, 13, 31, 38, 48, 138, 144]. In addition, National Health Survey and Iowa both asked about time period of exposure [38, 136].

Military Health Study and Kansas II evaluated depleted uranium exposure using questions regarding contact with destroyed enemy vehicles (or inhalation of smoke from vehicles) that may have been struck with artillery rounds containing depleted uranium [14], and exposure to the Camp Doha fire. They also asked whether participants had undergone a urine test for the presence of depleted uranium, the timing and provider of the test, and the results [35].

Sources of infection or contaminants

Many of the studies surveyed their participants regarding exposure to potential sources of infection or contamination, which included food, water, pesticides, and local fauna. The response formats for most of the questions were at least binary [10, 12–14, 25, 32, 33, 35, 38, 48, 51, 136, 138, 142]. Similar question phrasing was used for National Health Survey, Iowa, and the VA Registry [38, 48, 136] and furthermore, National Health Survey and Iowa used the same three-point scale to describe the length of exposure [38, 136]. Devens and a New Orleans subset also used identical tools to evaluate exposures [3, 25, 45]. Additional exposure information was gathered in three studies. A VA registry subset was asked about the frequency of each exposure’s occurrence [51]. Devens inquired about water and pesticide use, including source of drinking water, unusual smell or tastes in the water, any illnesses or health problems caused by the drinking water, pesticide name, who sprayed the pesticide, presence of any acute symptoms, and exposure frequency [25]. Military Health Study also asked questions about frequency and quantity of application [35].

Psychological trauma

The experiencing of psychologically stressful events was one of the primary factors surveyed in the initial studies of veterans of the Gulf War. The perceived importance of this factor is demonstrated by its inclusion in all of the studies except Kansas I. The most commonly studied items were life events and combat-related stressors, the latter of which included direct combat duty, witnessing of casualties, POW contact, physical injury, and the experience of sexual harassment and/or sexual assault or rape.

Because combat-related traumatic events have long been recognized for their effects on psychological health, some tools for their assessment existed at the initiation of the Gulf War studies. Instruments used in these studies included the Combat Exposure Scale [191, 192], the Mississippi Scale (Operation Desert Storm version) [183], the Keane Combat Scale [193], the Operation Desert Storm Stress Exposure Scale [194], and the Haley Gulf War Combat Exposure Index [35]. With the exception of the Keane Combat Scale (used by Oregon-Washington, Military Health Study, and VA Registry), each instrument was used by only one study. In addition, many studies incorporated self-constructed questions regarding lifetime and combat-related stressors. Thus, creating a framework of direct comparability for this domain may be challenging.

Behavioral risk factors

All but Kansas I evaluated behavioral risk factors. The most common of these were alcohol and tobacco use. Alcohol use was primarily evaluated using self-constructed questions about current drinking status, alcohol abuse, and number of drinks consumed [2, 4, 10, 12, 13, 17, 25, 35, 45, 51, 195, 196]. However, Iowa, National Health Survey, and Millennium Cohort used validated instruments. Iowa used the CAGE (Cut back, Annoyance, Guilt, Eye-openers) questionnaire [2, 197], and both National Health Survey and Millennium Cohor used the alcohol component of the Patient Health Questionnaire [92].Tobacco use was most commonly queried by asking participants about their smoking status (never, past, or current smoker) [2–4, 10, 12–14, 17, 25, 35, 45, 48, 139, 198]. Additional information obtained varied by study, but included increases or decreases in daily smoking habits [198] and whether participants had smoked at least 100 cigarettes [51, 198].

Validation studies

The studies reviewed herein all gathered self-reported data, which has well-documented limitations, including recall bias and lack of correlation with objective measures. In light of these challenges to data quality, several studies performed reliability and validation analyses, using test-retest methods and comparing self-reported data to clinical evaluations and medical records.

Seabees, Iowa, Millennium Cohort, and Oregon-Washington measured the internal reliability of self-reported survey data, including demographics, physical and functional status, symptoms, health histories, vaccinations, and exposures, using test-retest methods. The results of these studies were mixed, particularly with respect to self-reported exposures, diagnosed health conditions, and symptoms. The Seabees study [31] reported high reliability of demographic attributes (kappas 0.89-1.00), and moderate reliability of exposures (0.60-0.70) and “other” survey items (0.51-0.67). However, self-reported diagnoses and symptoms had widely ranging kappa coefficients of −0.01-1.00 and −0.01-0.86, respectively [31]. The Iowa cohort reported test-retest agreement percentages of 89.6-97.0% and kappa coefficients of 0.39-0.70 for self-reported medical and psychiatric concerns [2]. In the Oregon-Washington evaluation of self-reported exposure reliability, only eight of thirteen exposures had a kappa coefficient statistically greater than 0.4, reflecting poor agreement on the majority of measures [32]. The Oregon-Washington investigators also assessed self-reported exposure misclassification by comparing reported exposure to anthrax and botulinum toxoid vaccines, chemical warfare agents, and pyridostigmine bromide to reported deployment periods, as each exposure was only possible during known periods of time. The results of this comparison suggested that these exposures may be overreported among certain subgroups of veterans [32]. Similarly, an analysis of National Health Survey data found evidence of reporting bias in self-reported anthrax vaccination data [199]. We note that it has been difficult to validate reported exposures due to the absence of objective documentation.

Clinical evaluations and medical records were used to externally validate self-reported information by several studies. As was the case for test-retest reliability analyses, the results were mixed. A New Orleans substudy examined the validity of survey-based PTSD assessments by calculating the agreement between the Structured Clinical Interview for DSM-III-R (SCID) and other PTSD diagnostic measures (agreement 82-100%) [44]. The Seabees validation study, which compared personnel and medical records to survey responses, found kappa coefficients of −0.02-0.48 for self-reported diagnosed illness, 0.41-0.76 for demographic traits, and 0.59-0.66 for “other” characteristics [31]. In the National Health Survey, comparison of reported reasons for clinic visits and hospitalizations to medical records found agreement rates greater than 90% [10, 29], and clinical evaluations confirmed an increased risk of certain conditions among deployed veterans [53]. The Iowa study drew on state registries to validate reported birth defects and cancers [60]. In addition, a case validation study in a subset of Iowa cohort members found that only 32% of those who originally reported depressive symptoms met criteria for lifetime depression after a later SCID-IV interview; however, multiple factors may have contributed to this difference [200]. The Millennium Cohort found excellent negative agreement (generally > 95%) and moderate positive agreement when comparing self-reported medical conditions to Department of Defense electronic medical records, suggesting that self-reported data may be useful in excluding the presence of conditions [146]. Finally, in a small-sample comparison of thirteen self-reported medical conditions to medical records, the Devens Cohort Study observed low-moderate kappa coefficients of 0.35-0.64 for most conditions [39]. These heterogeneous findings regarding reliability and validity lend support to concerns about the utility of self-reported data, and emphasize the importance of evaluating reliability and validity early in the study implementation period, and including objective data sources, when resources permit.

Conclusions

We compared the survey tools used in keystone epidemiologic studies and registries of Gulf War Era veterans, with the intent of highlighting commonalities and differences in efforts aimed at understanding health and risk factors. It is apparent that there are many areas of at least minimal concordance with respect to question and response format. We note that some investigators intentionally drew on the materials used by prior studies, establishing areas of commonality [1, 12, 60]. Among mental and physical health domains, there was moderate concordance among the measures used to assess medical history, symptoms, functional status, and the diagnoses of chronic fatigue syndrome and fibromyalgia. Most of the exposure assessment instruments also have response formats that can be reduced to the same binary framework. These similarities suggest that meta-analyses of study-level or individual-level data could be performed on several of the subdomains, with varying degrees of loss of detail.

In contrast, there is substantial variation in survey instruments for the subdomains of health status, PTSD, psychological status, psychological trauma, and the diagnoses of fatigue, multiple chemical sensitivity, and multisymptom illness. The nature of this variability differs by subdomain. While this does not preclude the use of meta-analytic techniques, it requires the analyst to carefully consider issues of heterogeneity and whether the instruments demonstrate convergent validity.

We cannot overemphasize the importance of considering the impact of heterogeneity in study design, population, sampling methods, quality, and generalizability to the validity of meta-analyses. While it is possible to carefully combine data from similarly-conducted epidemiologic studies [201], the practical reality is that explicitly accommodating design and quality differences to yield valid inference in analyses of this type remains an extremely difficult (at times impossible) task [202, 203]. In addition, restrictions on the sharing of study data may present a logistical challenge to the performance of individual-level joint analyses. This places additional emphasis on the need for investigators to consent future study participants using language that explicitly permits recontact for future studies or (at minimum) sharing of de-identified data under approved protocols for Gulf War Era related research.

Based on our review of the existing studies, we suggest three considerations for future studies of Gulf War Era veterans. First, to engage Gulf War Era research experts during study planning. Second, to gather blood for genetic and proteomic analyses, and link the specimens to survey and medical/administrative records. Third, to carefully consider the strengths and weaknesses of the survey instruments used in the past, and select instruments that are appropriately validated, detailed, and compatible with previous studies. These three activities will support the development of unified data and biospecimen resources with opportunities for analytic collaborations. Through such efforts, epidemiologic research can continue to make important strides that advance our collective ability to enhance the health of these veterans.

Disclaimer

The contents of this manuscript do not represent the views of the Department of Veterans Affairs or the United States Government.

Abbreviations

AF:

Air Force

CAGE:

Cut back, Annoying, Guilt, Eye-openers

CARC:

Chemical agent resistant coating

CFS:

Chronic fatigue syndrome

Com:

Commissioned officer

DoD:

United States Department of Defense

DSM-III-R:

Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised

FL:

Florida

GW:

Gulf War

HI:

Hawaii

KS:

Kansas

MA:

Massachusetts

MCS:

Multiple chemical sensitivity

MO:

Missouri

MRI:

Magnetic resonance imaging

MSI:

Multisymptom illness

NG:

National Guard

Noncom:

Noncommissioned officer

OIF:

Operation Iraqi Freedom

OMB:

Office of Management and Budget

OR:

Oregon

PA:

Pennsylvania

PTSD:

Post-traumatic stress disorder

POW:

Prisoner of war

Res:

Reserve service

SCID:

Structured clinical interview for DSM-III-R

Seabees:

Construction Battalion (CB)

SF:

Medical Outcomes Study Short Form Survey

SW:

Southwest

US:

United States of America

VA:

United States Department of Veterans Affairs

WA:

Washington.

References

  1. 1.

    Steele L: Prevalence and patterns of Gulf War illness in Kansas veterans: association of symptoms with characteristics of person, place, and time of military service. Am J Epidemiol. 2000, 152: 992-1002. 10.1093/aje/152.10.992.

  2. 2.

    The Iowa Persian Gulf Study Group: Self-reported illness and health status among Gulf War veterans: a population-based study. JAMA. 1997, 277: 238-245.

  3. 3.

    Proctor S: Health status of Persian Gulf War veterans: self-reported symptoms, environmental exposures, and the effect of stress. Int J Epidemiol. 1998, 27: 1000-1010. 10.1093/ije/27.6.1000.

  4. 4.

    Fukuda K, Nisenbaum R, Stewart G, Thompson W, Robin L, Washko R, Noah D, Barrett D, Randall B, Herwaldt B: Chronic multisymptom illness affecting Air Force veterans of the Gulf War. JAMA. 1998, 280: 981-988. 10.1001/jama.280.11.981.

  5. 5.

    Kang HK, Bullman TA: Mortality among U.S. veterans of the Persian Gulf War. N Engl J Med. 1996, 335: 1498-1504. 10.1056/NEJM199611143352006.

  6. 6.

    Gray GC, Kang HK: Healthcare utilization and mortality among veterans of the Gulf War. Philos Trans R Soc Lond B Biol Sci. 2006, 361: 553-569. 10.1098/rstb.2006.1816.

  7. 7.

    Wolfe J, Kelly JM, Bucsela ML: Fort Devens reunion survey: report of phase I. Returning Persian Gulf Troops: First Year Findings. 1992, West Haven: Department of Veterans Affairs, 19-44.

  8. 8.

    Brailey K, Vasterling J, Sutker P: Psychological Aftermath of Participation in the Persian Gulf War. The Environment and Mental Health: A Guide for Clinicians. Edited by: Lundberg A. 1998, Mahwah: Lawrence Erlbaum Associates, 83-101.

  9. 9.

    Murphy FM, Kang H, Dalager NA, Lee KY, Allen RE, Mather SH, Kizer KW: The health status of Gulf War veterans: lessons learned from the Department of Veterans Affairs Health Registry. Mil Med. 1999, 164: 327-331.

  10. 10.

    Kang H, Mahan CM, Lee KY, Magee CA, Murphy FM: Illnesses among United States veterans of the Gulf War: a population-based survey of 30,000 veterans. J Occup Environ Med. 2000, 42: 491-501. 10.1097/00043764-200005000-00006.

  11. 11.

    Stuart JA, Murray KM, Ursano RJ, Wright KM: The Department of Defense's Persian Gulf War registry year 2000: an examination of veterans' health status. Mil Med. 2002, 167: 121-128.

  12. 12.

    Gray GC, Reed RJ, Kaiser KS, Smith TC, Gastanaga VM: Self-reported symptoms and medical conditions among 11,868 Gulf War-era veterans: the Seabee Health Study. Am J Epidemiol. 2002, 155: 1033-1044. 10.1093/aje/155.11.1033.

  13. 13.

    Spencer PS, McCauley LA, Lapidus JA, Lasarev M, Joos SK, Storzbach D: Self-reported exposures and their association with unexplained illness in a population-based case–control study of Gulf War veterans. J Occup Environ Med. 2001, 43: 1041-1056.

  14. 14.

    Steele L, Sastre A, Gerkovich MM, Cook MR: Complex factors in the etiology of Gulf War Illness: wartime exposures and risk factors in veteran subgroups. Environ Health Perspect. 2012, 120: 112-118.

  15. 15.

    Smith B, Leard CA, Smith TC, Reed RJ, Ryan MA: Anthrax vaccination in the Millennium Cohort: validation and measures of health. Am J Prev Med. 2007, 32: 347-353. 10.1016/j.amepre.2006.12.015.

  16. 16.

    Iannacchione VG, Dever JA, Bann CM, Considine KA, Creel D, Carson CP, Best H, Haley RW: Validation of a research case definition of Gulf War Illness in the 1991 US military population. Neuroepidemiology. 2011, 37: 129-140. 10.1159/000331478.

  17. 17.

    Stretch RH, Bliese PD, Marlowe DH, Wright KM, Knudson KH, Hoover CH: Physical health symptomatology of Gulf War-era service personnel from the states of Pennsylvania and Hawaii. Mil Med. 1995, 160: 131-136.

  18. 18.

    National Institute of Health: The Persian Gulf experience and health: NIH Technology Assessment Workshop Panel. JAMA. 1994, 272: 391-396. 10.1001/jama.1994.03520050071033.

  19. 19.

    Persian Gulf Veterans Coordinating Board: Unexplained illnesses among Desert Storm veterans: a search for causes, treatment, and cooperation. Arch Intern Med. 1995, 155: 262-268. 10.1001/archinte.1995.00430030050005.

  20. 20.

    Institute of Medicine: Health Consequences of Service During the Persian Gulf War: Recommendations for Research and Information Systems. 1996, Washington: The National Academies Press

  21. 21.

    Institute of Medicine: Gulf War and Health. 1–8 volumes. 2000–2010, Washington: The National Academies Press

  22. 22.

    Institute of Medicine: Gulf War and Health, Volume 8: Update of Health Effects of Serving in the Gulf War. 2010, Washington: The National Academies Press

  23. 23.

    Research Advisory Committee on Gulf War Veterans' Illnesses: Gulf War Illness and the Health of Gulf War Veterans: Scientific Findings and Recommendations. 2008, Washington: U.S. Department of Veterans Affairs

  24. 24.

    Hallman WK, Kipen HM, Diefenbach M, Boyd K, Kang H, Leventhal H, Wartenberg D: Symptom patterns among Gulf War registry veterans. Am J Public Health. 2003, 93: 624-630. 10.2105/AJPH.93.4.624.

  25. 25.

    White R, Wolfe J, Proctor S, Keane TM: Devens Cohort Study: Time 3. 1994–1996, Boston: Boston Environmental Hazards Center and National Center for PTSD, Department of Veterans Affairs, VA Boston Healthcare System

  26. 26.

    Wolfe J, Mark W, Keane T: Ft. Devens ODS Reunion Survey: Time 2. 1991–1993, Boston: National Center for PTSD, Behavioral Science Division, Department of Veterans Affairs, VA Boston Healthcare System

  27. 27.

    Wolfe J, Mark W, Keane T: Ft. Devens ODS Reunion Survey: Time 1. 1991–1993, Boston: National Center for PTSD, Behavioral Science Division, Department of Veterans Affairs, VA Boston Healthcare System

  28. 28.

    Committee on the Evaluation of the Department of Veterans Affairs Uniform Case Assessment Protocol (Institute of Medicine): Adequacy of the VA Persian Gulf Registry and Uniform Case Assessment Protocol. 1998, Washington: National Academies Press

  29. 29.

    Kang H, Li B, Mahan CM, Eisen SA, Engel CJ: Health of US veterans of 1991 Gulf War: a follow-up survey in 10 years. J Occup Environ Med. 2009, 51: 401-410. 10.1097/JOM.0b013e3181a2feeb.

  30. 30.

    Joseph SC, Comprehensive Clinical Evaluation Program Evaluation Team: A comprehensive clinical evaluation of 20,000 Persian Gulf War veterans. Mil Med. 1997, 162: 149-155.

  31. 31.

    Gray GC, Kaiser KS, Hawksworth AW, Hall FW, Barrett-Connor E: Increased postwar symptoms and psychological morbidity among U.S. Navy Gulf War veterans. Am J Trop Med Hyg. 1999, 60: 758-766.

  32. 32.

    McCauley LA, Joos SK, Spencer PS, Lasarev M, Shuell T, Members of the Portland Environmental Hazards Research Center: Strategies to assess validity of self-reported exposures during the Persian Gulf War. Environ Res. 1999, 81: 195-205. 10.1006/enrs.1999.3977.

  33. 33.

    Centers for Disease Control and Prevention: Unexplained illness among Persian Gulf War veterans in an Air National Guard Unit: preliminary report--August 1990-March 1995. MMWR. 1995, 44: 443-447.

  34. 34.

    Gray GC, Chesbrough KB, Ryan MA, Amoroso P, Boyko EJ, Gackstetter GD, Hooper TI, Riddle JR: The Millennium Cohort Study: a 21-year prospective cohort study of 140,000 military personnel. Mil Med. 2002, 167: 483-488.

  35. 35.

    Department of Veterans Affairs: VA Contract V549P-0027: Gulf War Veterans' Illnesses Research, Task Order 2. 2007–2010, Washington: Awarded to University of Texas, Southwestern

  36. 36.

    Department of Veterans Affairs Office of Inspector General: Review of Contract No. VA549-P-0027 Between the Department of Veterans Affairs and The University of Texas Southwestern Medical Center at Dallas (UTSWMC) for Gulf War Illness Research. 2009, Washington: VA Office of Inspector General

  37. 37.

    Smith TC, Smith B, Ryan MA, Gray GC, Hooper TI, Heller JM, Dalager NA, Kang HK, Gackstetter GD: Ten years and 100,000 participants later: occupational and other factors influencing participation in US Gulf War health registries. J Occup Environ Med. 2002, 44: 758-768.

  38. 38.

    Carney CP, Sampson TR, Voelker M, Woolson R, Thorne P, Doebbeling BN: Women in the Gulf War: combat experience, exposures, and subsequent health care use. Mil Med. 2003, 168: 654-661.

  39. 39.

    Proctor SP, Harley R, Wolfe J, Heeren T, White RF: Health-related quality of life in Persian Gulf War veterans. Mil Med. 2001, 166: 510-519.

  40. 40.

    Wolfe J, Proctor SP, Keane TM: Devens Cohort Study: Time 4. 1997–1998, Boston: Boston Environmental Hazards Center and National Center for PTSD, Department of Veterans Affairs, VA Boston Healthcare System

  41. 41.

    Proctor S, Heaton KJ, White RF, Wolfe J: Chemical sensitivity and chronic fatigue syndrome in Gulf War veterans: a brief report. J Occup Environ Med. 2001, 43: 359-364.

  42. 42.

    Lindem K, Heeren T, White RF, Proctor SP, Krengel M, Vasterling JJ, Sutker PB, Wolfe J, Keane TM: Neuropsychological performance in Gulf War era veterans: traumatic stress symptomatology and exposure to chemical–biological warfare agents. J Psychopathol Behav. 2003, 25: 105-119. 10.1023/A:1023394932263.

  43. 43.

    Heaton KJ, Palumbo CL, Proctor SP, Killiany RJ, Yurgelun-Todd DA, White RF: Quantitative magnetic resonance brain imaging in US Army veterans of the 1991 Gulf War potentially exposed to sarin and cyclosarin. Neurotoxicology. 2007, 28: 761-769. 10.1016/j.neuro.2007.03.006.

  44. 44.

    Sutker PB, Uddo M, Brailey K, Allain AN, Errera P: Psychological symptoms and psychiatric diagnoses in Operation Desert Storm troops serving graves registration duty. J Trauma Stress. 1994, 7: 159-171. 10.1002/jts.2490070202.

  45. 45.

    Vasterling JJ, Brailey K, Tomlin H, Rice J, Sutker PB: Olfactory functioning in Gulf War-era veterans: relationships to war-zone duty, self-reported hazards exposures, and psychological distress. J Int Neuropsychol Soc. 2003, 9: 407-418.

  46. 46.

    Sutker PB, Davis JM, Uddo M, Ditta SR: War zone stress, personal resources, and PTSD in Persian Gulf War returnees. J Abnorm Psychol. 1995, 104: 444-452.

  47. 47.

    Vasterling JJ, Brailey K, Constans JI, Sutker PB: Attention and memory dysfunction in posttraumatic stress disorder. Neuropsychology. 1998, 12: 125-133.

  48. 48.

    Department of Veterans Affairs. Persian Gulf Registry Code Sheet. Form 10-9009a.http://www.gulflink.org/gwr/10-9009a.pdf,

  49. 49.

    Fiedler N, Giardino N, Natelson B, Ottenweller JE, Weisel C, Lioy P, Lehrer P, Ohman-Strickland P, Kelly-McNeil K, Kipen H: Responses to controlled diesel vapor exposure among chemically sensitive Gulf War veterans. Psychosom Med. 2004, 66: 588-598. 10.1097/01.psy.0000127872.53932.75.

  50. 50.

    Kipen HM, Hallman W, Kang H, Fiedler N, Natelson BH: Prevalence of chronic fatigue and chemical sensitivities in Gulf Registry veterans. Arch Environ Health. 1999, 54: 313-318. 10.1080/00039899909602493.

  51. 51.

    Boyd KC, Hallman WK, Wartenberg D, Fiedler N, Brewer NT, Kipen HM: Reported exposures, stressors, and life events among Gulf War Registry veterans. J Occup Environ Med. 2003, 45: 1247-1256. 10.1097/01.jom.0000099980.38936.09.

  52. 52.

    Koch TR, Emory TS: Evaluation of chronic gastrointestinal symptoms following Persian Gulf War exposure. Mil Med. 2005, 170: 696-700.

  53. 53.

    Eisen SA, Kang H, Murphy FM, Blanchard M, Reda DJ, Henderson W, Toomey R, Jackson L, Alpern R, Parks B: Gulf War veterans' health: medical evaluation of a U.S. cohort. Ann Intern Med. 2005, 142: 881-890.

  54. 54.

    Toomey R, Kang H, Karlinsky JB, Baker D, Vasterling J, Alpern R, Reda DJ, Henderson W, Murphy FM, Eisen SA: Mental health of US Gulf War veterans 10 years after the war. Brit J Psychiat. 2007, 190: 385-393. 10.1192/bjp.bp.105.019539.

  55. 55.

    Toomey R, Alpern R, Vasterling J, Baker D, Reda DJ, Lyons M, Henderson W, Kang H, Eisen SA, Murphy FM: Neuropsychological functioning of U.S. Gulf War veterans 10 years after the war. J Int Neuropsych Soc. 2009, 15: 717-729. 10.1017/S1355617709990294.

  56. 56.

    Wallin MT, Wilken J, Alfaro MH, Rogers C, Mahan C, Chapman JC, Fratto T, Sullivan C, Kang H, Kane R: Neuropsychologic assessment of a population-based sample of Gulf War veterans. Cogn Behav Neurol. 2009, 22: 155-166. 10.1097/WNN.0b013e3181b278e8.

  57. 57.

    Roy MJ, Koslowe PA, Kroenke K, Magruder C: Signs, symptoms, and ill-defined conditions in Persian Gulf War veterans: findings from the Comprehensive Clinical Evaluation Program. Psychosom Med. 1998, 60: 663-668.

  58. 58.

    Stretch RH, Marlowe DH, Wright KM, Bliese PD, Knudson KH, Hoover CH: Post-traumatic stress disorder symptoms among Gulf War veterans. Mil Med. 1996, 161: 407-410.

  59. 59.

    Stretch RH, Bliese PD, Marlowe DH, Wright KM, Knudson KH, Hoover CH: Psychological health of Gulf War-era military personnel. Mil Med. 1996, 161: 257-261.

  60. 60.

    Doebbeling BN, Jones MF, Hall DB, Clarke WR, Woolson RF, Torner JC, Burmeister LF, Snyders-Crumley T, Barrett DH, Falter KH: Methodologic issues in a population-based health survey of Gulf War veterans. J Clin Epidemiol. 2002, 55: 477-487. 10.1016/S0895-4356(01)00517-0.

  61. 61.

    Barrash J, Denburg NL, Moser DJ, Woolson RF, Schumacher AJ, Doebbeling BN: Credibility of neuropsychological performances of Persian Gulf War veterans and military control subjects participating in clinical epidemiological research. Mil Med. 2007, 172: 697-707.

  62. 62.

    Bourdette DN, McCauley LA, Barkhuizen A, Johnston W, Wynn M, Joos SK, Storzbach D, Shuell T, Sticker D: Symptom factor analysis, clinical findings, and functional status in a population-based case control study of Gulf War unexplained illness. J Occup Environ Med. 2001, 43: 1026-1040.

  63. 63.

    Storzbach D, Rohlman DS, Anger WK, Binder LM, Campbell KA: Neurobehavioral deficits in Persian Gulf veterans: additional evidence from a population-based study. Environ Res. 2001, 85: 1-13. 10.1006/enrs.2000.4100.

  64. 64.

    Smith TC, Wingard DL, Ryan MA, Kritz-Silverstein D, Slymen DJ, Sallis JF: PTSD prevalence, associated exposures, and functional health outcomes in a large, population-based military cohort. Public Health Rep. 2009, 124: 90-102.

  65. 65.

    Proctor S, Wells TS, Jones KA, Boyko EJ, Smith TC: Examination of post-service health-related quality of life among rural and urban military members of the Millennium Cohort Study. J Rur Soc Sci. 2011, 26: 32-56.

  66. 66.

    Cutrona CE: Social support and stress in the transition to parenthood. J Abnorm Psychol. 1984, 93: 378-390.

  67. 67.

    Cutrona CE, Russell D: The provisions of social relationships and adaptation to stress. Advances in Personal Relationships. Edited by: Jones WH, Perlman D. 1987, Greenwich: JAI Press, 37-67. 1

  68. 68.

    Holahan CJ, Moos RH: Life stressors, personal and social resources, and depression: a 4-year structural model. J Abnorm Psychol. 1991, 100: 31-38.

  69. 69.

    Sarason IG, Sarason BR, Shearin EN, Pierce GR: A brief measure of social support: practical and theoretical implications. J Soc Pers Relat. 1987, 4: 497-510. 10.1177/0265407587044007.

  70. 70.

    Steiner A, Raube K, Stuck AE, Aronow HU, Draper D, Rubenstein LZ, Beck JC: Measuring psychosocial aspects of well-being in older community residents: performance of four short scales. Gerontologist. 1996, 36: 54-62. 10.1093/geront/36.1.54.

  71. 71.

    McCubbin HI, Thompson AI, McCubbin MA: Family Assessment: Resiliency, Coping, and Adaptation-Inventories for Research and Practice. Family Inventory of Life Events and Changes. Edited by: McCubbin HI, Patterson J, Wilson L. 1996, Madison: University of Wisconsin System, 103-178.

  72. 72.

    Olson DH, Bell R, Portner J: FACES II: Family Adaptibility and Cohesion Evaluation Scale. Family Inventories. Edited by: Olson D, McCubbin HI, Barnes LA, Musen M, Wilson M. 1982, St. Paul: Department of Family Social Science, University of Minnesota

  73. 73.

    Kukla R, Schlenger W, Fairbank J, Hough R, Jordan B, Marmar C, Weiss D: Trauma and the Vietnam War Generation: Report of Findings from the National Vietnam Veterans' Readjustment Study (NVVRS). 1990, New York: Brunner/Mazel

  74. 74.

    Nelson H: The National Adult Reading Test (NART): Test Manual. 1982, Windsor: NFER

  75. 75.

    Wechsler D: Manual for the Wechsler Adult Intelligence Scale. 1945, New York: Psychological Corporation

  76. 76.

    Shipley W: A self-administering scale for measuring intellectual impairment and deterioration. J Psychol. 1940, 9: 371-377. 10.1080/00223980.1940.9917704.

  77. 77.

    Shipley W: Institute of Living Scale. 1946, Los Angeles: Western Psychological Services

  78. 78.

    Costa PT, McCrae RR: The NEO Personality Inventory Manual. 1985, Odessa: Psychological Assessment Resources

  79. 79.

    Bartone PT, Ursano RJ, Wright KM, Ingraham LH: The impact of a military air disaster on the health of assistance workers. A prospective study. J Nerv Ment Dis. 1989, 177: 317-328. 10.1097/00005053-198906000-00001.

  80. 80.

    Eysenck HJ, Eysenck SBG: Manual of the Eysenck Personality Questionnaire. 1975, London: Hodder and Stoughton

  81. 81.

    Derogatis LR, Lipman RS, Rickels K, Uhlenhuth EH, Covi L: The Hopkins Symptom Checklist (HSCL): a self-report symptom inventory. Behav Sci. 1974, 19: 1-15. 10.1002/bs.3830190102.

  82. 82.

    Derogatis LR, Rickels K, Uhlenhuth EH, Covi L: The Hopkins Symptom Checklist: A Measure of Primary Symptom Dimensions. Psychological Measurements in Psychopharmacology. Edited by: Pichot P. 1974, Paris: Karger, 79-110. 7

  83. 83.

    Butcher JN, Dahlstrom WG, Tellegen A, Kaemmer B: Minnesota Multiphasic Personality Inventory-2: Manual for Administration and Scoring. 1989, Minneapolis: University of Minnesota Press

  84. 84.

    Morey L: The Personality Assessment Inventory Professional Manual. 1991, Lutz: Psychological Assessment Resources

  85. 85.

    Andrews G, Peters L: The psychometric properties of the Composite International Diagnostic Interview. Soc Psychiatry Psychiatr Epidemiol. 1998, 33: 80-88. 10.1007/s001270050026.

  86. 86.

    Derogatis LR: The Symptoms Checklist-90. 1983, Towson: Clinical Psychometric Research

  87. 87.

    Robins L, Helzer J: Diagnostic interview schedule (DIS), version III-R. 1991, St. Louis: Washington University School of Medicine

  88. 88.

    Derogatis LR, Spencer PM: The Brief Symptom Inventory (BSI): Administration, Scoring and Procedures Manual. 1982, Baltimore: Clinical Psychometric Research

  89. 89.

    Derogatis LR, Melisaratos N: The Brief Symptom Inventory: an introductory report. Psychol Med. 1983, 13: 595-605. 10.1017/S0033291700048017.

  90. 90.

    Spitzer RL, Williams J, Gibbon M: Structured Clinical Interviews for DSM-III-R, Version NP-V. 1987, New York: Biometrics Research Department, New York State Psychiatric Institute

  91. 91.

    Kovera CA, Anger WK, Campbell KA, Binder LM, Storzbach D, Davis KL, Rohlman DS: Computer-administration of questionnaires: a health screening system (HSS) developed for veterans. Neurotoxicol Teratol. 1996, 18: 511-518. 10.1016/0892-0362(96)00042-6.

  92. 92.

    Spitzer RL, Kroenke K, Williams JB, Patient Health Questionnaire Primary Care Study Group: Validation and utility of a self-report version of PRIME-MD: the PHQ primary care study. JAMA. 1999, 282: 1737-1744. 10.1001/jama.282.18.1737.

  93. 93.

    Spitzer RL, Williams JB, Kroenke K, Linzer M, deGruy FV, Hahn SR, Brody D, Johnson JG: Utility of a new procedure for diagnosing mental disorders in primary care. The PRIME-MD 1000 study. JAMA. 1994, 272: 1749-1756. 10.1001/jama.1994.03520220043029.

  94. 94.

    Beck AT, Ward CH, Mendelson M, Mock J, Erbaugh J: An inventory for measuring depression. Arch Gen Psychiatry. 1961, 4: 561-571. 10.1001/archpsyc.1961.01710120031004.

  95. 95.

    Peterson RA, Reiss S: Anxiety Sensitivity Index Manual. 1987, Worthington: IDS Publishing

  96. 96.

    Beck AT, Epstein N, Brown G, Steer RA: An inventory for measuring clinical anxiety: psychometric properties. J Consult Clin Psychol. 1988, 56: 893-897.

  97. 97.

    Beck AT, Steer RA: Beck Anxiety Inventory Manual. 1993, San Antonio: Psychological Corporation Harcourt

  98. 98.

    Spielberger CD, Sydeman SJ: State-Trait Anxiety Inventory and State-Trait Anger Expression. The Use of Psychological Testing for Treatment Planning and Outcome Assessment. Edited by: Maruish ME. 1994, Hillsdale: L. Erlbaum Associates, 292-321.

  99. 99.

    Delis DC, Kramer JH, Kaplan E, Ober B: California Verbal Learning Test Manual. 1987, New York: Psychological Corporation

  100. 100.

    Rey A: L'examen clinique en psychologic. [The clinical examination in psychology]. 1964, Paris: Presses Universitaires de France

  101. 101.

    Schmidt M: Rey Auditory Verbal Learning Test: A Handbook. 1996, Los Angeles: Western Psychological Services

  102. 102.

    Tombaugh TN: Test of Memory and Malingering. 1996, Toronto: Multi-Health Systems, Inc

  103. 103.

    Wechsler D: A standardized memory scale for clinical use. J Psychol. 1945, 19: 87-95. 10.1080/00223980.1945.9917223.

  104. 104.

    Wechsler D: Wechsler Memory Scale, Third Edition Manual. 1997, San Antonio: Psychological Corporation

  105. 105.

    Warrington E: The Recognition Memory Test: Manual. 1984, London: NFER-Nelson

  106. 106.

    Heaton R, Grant I, Matthews C: Comprehensive Norms for an Expanded Halstead-Reitan Battery: Demographic Corrections, Research Findings, and Clinical Applications. 1991, Odessa: Psychological Assessment Resources Inc

  107. 107.

    Trahan DE, Larrabee GJ: Continuous Visual Memory Test Professional Manual. 1988, Odessa: Psychological Assessment Resources

  108. 108.

    Barrash J, Suhr J, Manzel K: Detecting poor effort and malingering with an expanded version of the Auditory Verbal Learning Test (AVLTX): validation with clinical samples. J Clin Exp Neuropsychol. 2004, 26: 125-140. 10.1076/jcen.26.1.125.23928.

  109. 109.

    Reitan R, Wolfson D: The Halstead-Reitan Neuropsychological Test Battery: Theory and Clinical Interpretation. 1985, Tucson: Neuropsychology Press

  110. 110.

    Army Individual Test Battery: Manual of Directions and Scoring. 1944, Washington: War Department, Adjutant General's Office

  111. 111.

    Conners CK: Conners' Continuous Performance Test Computer Program User's Guide. 1992, Toronto: Multi-Health Systems

  112. 112.

    Kay GG, Berman B, Mockoviak SH, Morris CE, Reeves D, Starbuck V, Sukenik E, Harris AG: Initial and steady-state effects of diphenhydramine and loratadine on sedation, cognition, mood, and psychomotor performance. Arch Intern Med. 1997, 157: 2350-2356. 10.1001/archinte.1997.00440410082009.

  113. 113.

    Broadbent DE, Cooper PF, FitzGerald P, Parkes KR: The Cognitive Failures Questionnaire (CFQ) and its correlates. Br J Clin Psychol. 1982, 21: 1-16. 10.1111/j.2044-8260.1982.tb01421.x.

  114. 114.

    Berg EA: A simple objective technique for measuring flexibility in thinking. J Gen Psychol. 1948, 39: 15-22. 10.1080/00221309.1948.9918159.

  115. 115.

    Stroop JR: Studies of interference in serial verbal reactions. J Exp Psychol. 1935, 18: 643-661.

  116. 116.

    Mills KC, Parkman KM, Spruill SE: A PC-based software test for measuring alcohol and drug effects in human subjects. Alcohol Clin Exp Res. 1996, 20: 1582-1591. 10.1111/j.1530-0277.1996.tb01703.x.

  117. 117.

    Shin MS, Park SY, Park SR, Seol SH, Kwon JS: Clinical and empirical applications of the Rey-Osterrieth Complex Figure Test. Nat Protoc. 2006, 1: 892-899. 10.1038/nprot.2006.115.

  118. 118.

    Rey A: L’examen psychologique dans les cas d’encephalopathie traumatique [The psychological examination in cases of traumatic encephalopathy]. Arch Psychol. 1941, 28: 286-340.

  119. 119.

    Gronwall DM: Paced auditory serial-addition task: a measure of recovery from concussion. Percept Mot Skills. 1977, 44: 367-373. 10.2466/pms.1977.44.2.367.

  120. 120.

    Benton AL, Hamsher KDS: Multilingual Aphasia Examination. 1976, Iowa City: AJA Associates, 2

  121. 121.

    Letz R: NES2 User's Manual (version 4.4). 1991, Winchester: Neurobehavioral Systems, Inc

  122. 122.

    Anger WK, Rohlman DS, Sizemore OJ, Kovera CA, Gibertini M, Ger J: Human behavioral assessment in neurotoxicology: producing appropriate test performance with written and shaping instructions. Neurotoxicol Teratol. 1996, 18: 371-379. 10.1016/0892-0362(96)00037-2.

  123. 123.

    Smith A: SDMT: A neuropsychological test for economic screening. Hear Disord. 1968, 3: 83-91.

  124. 124.

    Posner MI: Chronometric Explorations of Mind. 1978, Hillside: Erlbaum

  125. 125.

    Binder LM, Willis SC: Assessment of motivation after financially compensable minor head trauma. Psychol Assess. 1991, 3: 175-181.

  126. 126.

    Klove H: Clinical neuropsychology. Med Clin North Am. 1963, 47: 1647-1658.

  127. 127.

    Tiffin J: Purdue Pegboard Examiner's Manual. 1968, Rosemont: London House

  128. 128.

    Halstead WC: Brain and Intelligence. 1947, Chicago: University of Chicago Press

  129. 129.

    Bergner M, Bobbitt RA, Kressel S, Pollard WE, Gilson BS, Morris JR: The sickness impact profile: conceptual formulation and methodology for the development of a health status measure. Int J Health Serv. 1976, 6: 393-415. 10.2190/RHE0-GGH4-410W-LA17.

  130. 130.

    Gilson BS, Gilson JS, Bergner M, Bobbit RA, Kressel S, Pollard WE, Vesselago M: The sickness impact profile: development of an outcome measure of health care. Am J Public Health. 1975, 65: 1304-1310. 10.2105/AJPH.65.12.1304.

  131. 131.

    Barsky AJ, Wyshak G, Klerman GL: The somatosensory amplification scale and its relationship to hypochondriasis. J Psychiatr Res. 1990, 24: 323-334. 10.1016/0022-3956(90)90004-A.

  132. 132.

    Pilowsky I, Spence N: Manual for the Illness Behavior Questionnaire. 1994, South Australia: Department of Psychiatry, University of Adelaide, 3

  133. 133.

    Frisch MB: Manual and Treatment Guide for the Quality of Life Inventory. 1994, Minneapolis: National Computer Systems

  134. 134.

    Wolfe J, Proctor SP, Erickson DJ, Hu H: Risk factors for multisymptom illness in US Army veterans of the Gulf War. J Occup Environ Med. 2002, 44: 271-281. 10.1097/00043764-200203000-00015.

  135. 135.

    Follow-up of Psychological and Neurocognitive Gulf War Outcome: Relation to Stress.http://webcache.googleusercontent.com/search?q=cache:crtS-W6PyecJ:http://fhp.osd.mil/deploymed/projectDetail.jsp%3FprojectId%3D527%26region%3D0%26researchTopic%3D2%26majorDeployment%3D0%26researchSubTopic%3D10%2Bdeploymed+project+detail+527&rls=com.microsoft%3A*&oe=UTF-8&startIndex=&startPage=1&gs_l=heirloom-serp.3..5516.5704.0.6704.2.2.0.0.0.0.0.0.0.0..0.0..1c.1.Asten6c5jYk&hl=en&nfpr=1&spell=&ct=clnk,

  136. 136.

    Department of Veterans Affairs: National Health Survey of Persian Gulf War Era Veterans Questionnaire. 1995, Washington: Department of Veterans Affairs

  137. 137.

    Blanchard M, Eisen SA, Alpern R, Karlinsky JB, Toomey R, Reda DJ, Murphy FM, Jackson L, Kang H: Chronic multisymptom illness complex in Gulf War I veterans 10 years later. Am J Epidemiol. 2006, 163: 66-75.

  138. 138.

    Kroenke K, Koslowe P, Roy M: Symptoms in 18,495 Persian Gulf War veterans: latency of onset and lack of association with self-reported exposures. J Occup Environ Med. 1998, 40: 520-528. 10.1097/00043764-199806000-00004.

  139. 139.

    Cowan DN, Lange JL, Heller J, Kirkpatrick J, DeBakey S: A case–control study of asthma among U.S. Army Gulf War veterans and modeled exposure to oil well fire smoke. Mil Med. 2002, 167: 777-782.

  140. 140.

    Engel CC, Ursano R, Magruder C, Tartaglione R, Jing Z, Labbate LA, Debakey S: Psychological conditions diagnosed among veterans seeking Department of Defense care for Gulf War-related health concerns. J Occup Environ Med. 1999, 41: 384-392. 10.1097/00043764-199905000-00006.

  141. 141.

    Ford JD, Campbell KA, Storzbach D, Binder LM, Anger WK, Rohlman DS: Posttraumatic stress symptomatology is associated with unexplained illness attributed to Persian Gulf War military service. Psychosom Med. 2001, 63: 842-849.

  142. 142.

    Nisenbaum R, Barrett DH, Reyes M, Reeves WC: Deployment stressors and a chronic multisymptom illness among Gulf War veterans. J Nerv Ment Dis. 2000, 188: 259-266. 10.1097/00005053-200005000-00002.

  143. 143.

    Smith TC, Jacobson IG, Smith B, Hooper TI, Ryan MA, Team FT: The occupational role of women in military service: validation of occupation and prevalence of exposures in the Millennium Cohort Study. Int J Environ Health Res. 2007, 17: 271-284. 10.1080/09603120701372243.

  144. 144.

    Smith B, Smith TC, Gray GC, Ryan MA: When epidemiology meets the Internet: web-based surveys in the Millennium Cohort Study. Am J Epidemiol. 2007, 166: 1345-1354. 10.1093/aje/kwm212.

  145. 145.

    Jacobson IG, Smith TC, Smith B, Keel PK, Amoroso PJ, Wells TS, Bathalon GP, Boyko EJ, Ryan MA: Disordered eating and weight changes after deployment: longitudinal assessment of a large US military cohort. Am J Epidemiol. 2009, 169: 415-427.

  146. 146.

    Smith B, Chu LK, Smith TC, Amoroso PJ, Boyko EJ, Hooper TI, Gackstetter GD, Ryan MA: Challenges of self-reported medical conditions and electronic medical records among members of a large military cohort. BMC Med Res Methodol. 2008, 8: 37-10.1186/1471-2288-8-37.

  147. 147.

    Chyba M, Washington L: Questionnaires from the National Health Interview Survey, 1985–1989. Vital Health Stat. 1993, 1 (31):

  148. 148.

    Centers for Disease Control and Prevention: Behavioral Risk Factor Surveillance System Survey Questionnaire. 1995, Atlanta: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention

  149. 149.

    The University of Iowa: Female and family health questionnaire: the agricultural health study. 1993, Iowa City: University of Iowa

  150. 150.

    Agricultural Health Study.http://aghealth.nci.nih.gov/questionnaires.html,

  151. 151.

    Jacobson IG, White MR, Smith TC, Smith B, Wells TS, Gackstetter GD, Boyko EJ: Self-reported health symptoms and conditions among complementary and alternative medicine users in a large military cohort. Ann Epidemiol. 2009, 19: 613-622. 10.1016/j.annepidem.2009.05.001.

  152. 152.

    Cameron L, Leventhal EA, Leventhal H: Seeking medical care in response to symptoms and life stress. Psychosom Med. 1995, 57: 37-47.

  153. 153.

    Department of Veterans Affairs: Longitudinal Health Study of Persian Gulf War Era Veterans Questionnaire. 2002, Washington: Department of Veterans Affairs

  154. 154.

    Stouffer S, Guttman L, Suchman E: Studies in Social Psychology in World War II: Measurement and Prediction. 1950, Princeton: Princeton University Press

  155. 155.

    Bradburn N: The Structure of Psychological Well-Being. 1969, Chicago: Aldine

  156. 156.

    Kroenke K, Spitzer RL, Williams JB: The PHQ-15: validity of a new measure for evaluating the severity of somatic symptoms. Psychosom Med. 2002, 64: 258-266.

  157. 157.

    Lange JL, Schwartz DA, Doebbeling BN, Heller JM, Thorne PS: Exposures to the Kuwait oil fires and their association with asthma and bronchitis among Gulf War veterans. Environ Health Perspect. 2002, 110: 1141-1146. 10.1289/ehp.021101141.

  158. 158.

    Ferris BJ: Epidemiology standardization project. Am Rev Respir Dis. 1978, 118: 55-88.

  159. 159.

    Ware JE, Sherbourne CD: The MOS 36-item short-form health survey (SF-36). I. Conceptual framework and item selection. Med Care. 1992, 30: 473-483. 10.1097/00005650-199206000-00002.

  160. 160.

    Ware JE, Kosinski M, Dewey J: How to Score Version 2 of the SF-36 Health Survey. 2000, Lincoln: Quality Metric, Inc

  161. 161.

    Ware JE, Snow K, Kosinski M, Gandeck B: SF-36 Health Survey: Manual and Interpretation Guide. 1993, Boston: The Health Institute, New England Medical Center

  162. 162.

    Ware JE: SF-36 health survey update. Spine. 2000, 25: 3130-3139. 10.1097/00007632-200012150-00008.

  163. 163.

    Ware JE, Sherbourne CD, Davies AR: A Short-Form Health Survey (SF-36). 1988, New York: RAND Corporation

  164. 164.

    Feeny D, Furlong W, Torrance GW, Goldsmith CH, Zhu Z, DePauw S, Denton M, Boyle M: Multiattribute and single-attribute utility functions for the health utilities index mark 3 system. Med Care. 2002, 40: 113-128. 10.1097/00005650-200202000-00006.

  165. 165.

    Forman-Hoffman VL, Carney CP, Sampson TR, Peloso PM, Woolson RF, Black DW, Doebbeling BN: Mental health comorbidity patterns and impact on quality of life among veterans serving during the first Gulf War. Qual Life Res. 2005, 14: 2303-2314. 10.1007/s11136-005-6540-2.

  166. 166.

    Chalder T, Berelowitz G, Pawlikowska T, Watts L, Wessely S, Wright D, Wallace EP: Development of a fatigue scale. J Psychosom Res. 1993, 37: 147-153. 10.1016/0022-3999(93)90081-P.

  167. 167.

    Krupp LB, LaRocca NG, Muir-Nash J, Steinberg AD: The fatigue severity scale. Application to patients with multiple sclerosis and systemic lupus erythematosus. Arch Neurol. 1989, 46: 1121-1123. 10.1001/archneur.1989.00520460115022.

  168. 168.

    Smets EM, Garssen B, Bonke B, De Haes JC: The Multidimensional Fatigue Inventory (MFI): psychometric qualities of an instrument to assess fatigue. J Psychosom Res. 1995, 39: 315-325. 10.1016/0022-3999(94)00125-O.

  169. 169.

    Fukuda K, Straus SE, Hickie I, Sharpe MC, Dobbins JG, Komaroff A, International Chronic Fatigue Syndrome Study Group: The chronic fatigue syndrome: a comprehensive approach to its definition and study. Ann Intern Med. 1994, 121: 953-959.

  170. 170.

    Wolfe F, Ross K, Anderson J, Russell IJ, Hebert L: The prevalence and characteristics of fibromyalgia in the general population. Arthritis Rheum. 1995, 38: 19-28. 10.1002/art.1780380104.

  171. 171.

    Wolfe F, Smythe HA, Yunus MB, Bennett RM, Bombardier C, Goldenberg DL, Tugwell P, Campbell SM, Abeles M, Clark P: The American College of Rheumatology 1990 Criteria for the Classification of Fibromyalgia: Report of the Multicenter Criteria Committee. Arthritis Rheum. 1990, 33: 160-172. 10.1002/art.1780330203.

  172. 172.

    Szarek M, Bell I, Schwartz G: Validation of a brief screening measure of environmental chemical sensitivity: the Chemical Odor Intolerance Index. J Environ Psychol. 1997, 17: 345-351. 10.1006/jevp.1997.0071.

  173. 173.

    Kreutzer R, Neutra R, Lashuay N: Prevalence of people reporting sensitivities to chemicals in a population-based survey. Am J Epidemiol. 1999, 150: 1-12. 10.1093/oxfordjournals.aje.a009908.

  174. 174.

    Black DW, Doebbeling BN, Voelker MD, Clarke WR, Woolson RF, Barrett DH, Schwartz DA: Multiple chemical sensitivity syndrome: symptom prevalence and risk factors in a military population. Arch Intern Med. 2000, 160: 1169-1176. 10.1001/archinte.160.8.1169.

  175. 175.

    Kang H, Mahan CM, Murphy FM, Lee K, Simmens SJ, Young H, Levin P: Evidence of a deployment-related Gulf War syndrome by factor analysis. Arch Environ Health. 2002, 57: 61-68. 10.1080/00039890209602918.

  176. 176.

    Spencer PS, McCauley LA, Joos SK, Lasarev MR, Schuell T, Bourdette D, Barkhuizen A, Johnston W, Storzbach D, Wynn M: U.S. Gulf War veterans: service periods in theater, differential exposures, and persistent unexplained illness. Toxicol Lett. 1998, 102–103: 515-521.

  177. 177.

    Committee on Government Reform and Oversight: Gulf War Veterans' Illnesses: VA, DOD continue to resist strong evidence linking toxic causes to chronic health effects. HR 105–388. 1997, Washington: U.S. Government Printing Office

  178. 178.

    Blake DD, Weathers FW, Nagy L, Kaloupek DG, Klauminzer G, Charney DS: Clinician Administered PTSD Scale. 1990, West Haven: National Center for PTSD, Behavioral Sciences Division

  179. 179.

    Blake DD, Weathers FW, Nagy LM, Kaloupek DG, Gusman FD, Charney DS, Keane TM: The development of a Clinician-Administered PTSD Scale. J Trauma Stress. 1995, 8: 75-90. 10.1002/jts.2490080106.

  180. 180.

    Weathers FW, Huska JA, Keane TM: The PTSD Checklist- Military Version (PCL-M). 1991, Boston: National Center for PTSD

  181. 181.

    Weathers FW, Ford J: Psychometric Review of PTSD Checklist (PCL-C, PCL-S, PCL-M, PCL-PR). Measurement of Stress, Trauma, and Adaptation. Edited by: Stamm BH. 1996, Lutherville: Sidran Press

  182. 182.

    Wolfe J, Erickson DJ, Sharkansky EJ, King DW, King LA: Course and predictors of posttraumatic stress disorder among Gulf War veterans: a prospective analysis. J Consult Clin Psychol. 1999, 67: 520-528.

  183. 183.

    Keane TM, Caddell JM, Taylor KL: Mississippi Scale for Combat-Related Posttraumatic Stress Disorder: three studies in reliability and validity. J Consult Clin Psychol. 1988, 56: 85-90.

  184. 184.

    Spitzer RL, Williams JB, Gibbon M, First M: Structured Clinical Interview for DSM-III-R Patient Edition (SCID-P). 1989, New York: Biometrics Research Department, New York State Psychiatric Institute

  185. 185.

    Horowitz M, Wilner N, Alvarez W: Impact of Event Scale: a measure of subjective stress. Psychosom Med. 1979, 41: 209-218.

  186. 186.

    Phillips CJ, Matyas GR, Hansen CJ, Alving CR, Smith TC, Ryan MA: Antibodies to squalene in US Navy Persian Gulf War veterans with chronic multisymptom illness. Vaccine. 2009, 27: 3921-3926. 10.1016/j.vaccine.2009.03.091.

  187. 187.

    Chyba MM, Washington LR: Questionnaires from the National Health Interview Survey, 1985–89. Vital Health Stat. 1993, 1: 1-412.

  188. 188.

    Helmer DA, Flanagan ME, Woolson RF, Doebbeling BN: Health services use among Gulf War veterans and Gulf War era nondeployed veterans: a large population-based survey. Am J Public Health. 2007, 97: 2145-2148. 10.2105/AJPH.2006.104299.

  189. 189.

    Edwards W, Berlin M: In National Medical Expenditure Survey, Methods 2. Questionnaires and Data Collection Methods for the Household Survey and the Survey of American Indians and Alaska Natives. PHS 89–3450. 1989, Rockville: Public Health Service

  190. 190.

    Black DW, Doebbeling BN, Voelker MD, Clarke WR, Woolson RF, Barrett DH, Schwartz DA: Quality of life and health-services utilization in a population-based sample of military personnel reporting multiple chemical sensitivities. J Occup Environ Med. 1999, 41: 928-933. 10.1097/00043764-199910000-00014.

  191. 191.

    Gallops M, Laufer R, Yager T: Revised Combat Scale. Legacies of Vietnam: Comparative Adjustments of Veterans and Their Peers. Edited by: Laufer R, Yager T. 1981, Washington: US Government Printing Office, 3

  192. 192.

    Rosenheck R, Becnel H, Blank A, Farley F, Fontana A, Friedman MJ, Fulton J, Gelsomino J, Grishman M, Gusman FD: Returning Persian Gulf Troops: First-year Findings. Report of the Department of Veterans Affairs to the United States Congress on the Psychological Effects of the Persian Gulf War. 1992, West Haven: Evaluation Division of the National Center for PTSD, Department of Veterans Affairs

  193. 193.

    Keane TM, Fairbank J, Taylor KL, Mora C: Brief reports: clinical evaluation of a measure to assess combat exposure. Psychol Assessment. 1989, 1: 53-55.

  194. 194.

    Wolfe J: Applying principles of critical incident debriefing to the therapeutic management of acute combat stress. 1990, Boston: National Center for PTSD

  195. 195.

    Coughlin SS, Kang HK, Mahan CM: Alcohol use and selected health conditions of 1991 Gulf War veterans: survey results, 2003–2005. Prev Chronic Dis. 2011, 8: A52-

  196. 196.

    Jacobson IG, Ryan MA, Hooper TI, Smith TC, Amoroso PJ, Boyko EJ, Gackstetter GD, Wells TS, Bell NS: Alcohol use and alcohol-related problems before and after military combat deployment. JAMA. 2008, 300: 663-675. 10.1001/jama.300.6.663.

  197. 197.

    Ewing JA: Detecting alcoholism: the CAGE questionnaire. JAMA. 1984, 252: 1905-1907. 10.1001/jama.1984.03350140051025.

  198. 198.

    Smith B, Ryan MA, Wingard DL, Patterson TL, Slymen DJ, Macera CA: Cigarette smoking and military deployment: a prospective evaluation. Am J Prev Med. 2008, 35: 539-546. 10.1016/j.amepre.2008.07.009.

  199. 199.

    Mahan CM, Kang H, Dalager N, Heller JM: Anthrax vaccination and self-reported symptoms, functional status, and medical conditions in the National Health Survey of Gulf War Era Veterans and Their Families. Am J Epidemiol. 2004, 14: 81-88.

  200. 200.

    Black DW, Carney CP, Forman-Hoffman VL, Letuchy E, Peloso P, Woolson RF, Doebbeling BN: Depression in veterans of the first Gulf War and comparable military controls. Ann Clin Psychiatry. 2004, 16: 53-61. 10.1080/10401230490452645.

  201. 201.

    van der Steen JT, Kruse RL, Szafara KL, Mehr DR, van der Wal G, Ribbe MW, D'Agostino RB: Benefits and pitfalls of pooling datasets from comparable observational studies: combining US and Dutch nursing home studies. Palliat Med. 2008, 22: 750-759. 10.1177/0269216308094102.

  202. 202.

    Blettner M, Sauerbrei W, Schlehofer B, Scheuchenpflug T, Friedenreich C: Traditional reviews, meta-analyses and pooled analyses in epidemiology. Int J Epidemiol. 1999, 28: 1-9. 10.1093/ije/28.1.1.

  203. 203.

    Sutton AJ, Higgins JPT: Recent developments in meta-analysis. Stat Med. 2008, 27: 625-650. 10.1002/sim.2934.

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Acknowledgements

We are grateful for the helpful perspectives and materials provided by Drs. Jeannie Beckham, Nancy Crum-Cianflone, Scott McDonald, Susan Proctor, and Robert F. Woolson. Authors RBM, CMT, EH, MJ, and DP were supported by award #585, Cooperative Studies Program (CSP), Office of Research and Development, Veterans Health Administration, Department of Veterans Affairs. GDH manages the program that provides individual study funding, including CSP #585.

Author information

Affiliations

  1. Durham Epidemiologic Research and Information Center, Durham Veterans Affairs Medical Center, Durham, NC, USA

    • Rebecca B McNeil
    • , Catherine M Thomas
    • , Elizabeth Hauser
    •  & Dawn T Provenzale

  2. Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA, USA

    • Steven S Coughlin

  3. Department of Medicine, Duke University, Durham, NC, USA

    • Elizabeth Hauser
    •  & Dawn T Provenzale

  4. Cooperative Studies Program, Office of Research and Development, Department of Veterans Affairs, Washington, DC, USA

    • Grant D Huang

  5. Durham Veterans Affairs Medical Center, Durham, NC, USA

    • Karen M Goldstein
    •  & Dawn T Provenzale

  6. Health Services Research and Development, Durham Veterans Affairs Medical Center, Durham, NC, USA

    • Marcus R Johnson

  7. Clinical Informatics, Raleigh, NC, USA

    • Tyra Dunn-Thomas

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Corresponding author

Correspondence to Rebecca B McNeil.

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Competing interests

The authors declare that they have no competing interests.

Authors’ contributions

RBM co-directed the design and execution of the review, wrote the text, and approved the final version. CMT co-directed the design and execution of the review, wrote the text, and approved the final version. SSC contributed to the design of the review, wrote parts of the text, provided critical review, and approved the final version. EH contributed to the design of the review, wrote parts of the text, provided critical review, and approved the final version. GDH contributed to the design of the review, wrote parts of the text, provided critical review, and approved the final version. MJ contributed to the design of the review, wrote parts of the text, provided critical review, and approved the final version. KG contributed to the interpretation of the literature, wrote parts of the text, provided critical review, and approved the final version. TDT wrote part of the text, provided critical review, and approved the final version. DP contributed to the design of the review and the interpretation of the literature, wrote parts of the text, provided critical review, and approved the final version.

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Keywords

  • Persian Gulf War 1991
  • Survey methods
  • Blood banks

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