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Table 1 Characteristics of the study population stratified by categories of distance to the highway

From: Highway proximity associated with cardiovascular disease risk: the influence of individual-level confounders and exposure misclassification

  Within 50 m 50 m-150 m 150-250 m 250-450 m >1000 m
(N = 30) (N = 58) (N = 65) (N = 54) (N = 53)
Demographic variables
Age, mean (SD) 56.1 (11) 55.9 (11.36)# 61.9 (10.6)*# 58.6 (10.97) 56.7 (13.65)
BMI 31.9 (7.42)*# 27.7 (5.75)# 31.9 (7.85)*# 29.5 (7.65) 28.2 (7.58)
Female 57% 52% 58% 63% 68%
Born in USA
Yes 53% 71% 72% 57% 68%
Missing 10% 1% 3% 2% 4%
Race
White 67% 70% 65% 63% 64%
Non-white 30% 28% 34% 37% 36%
Missing 3% 2% 1% 0% 0%
Annual household income
Less than $24,999 27%# 26%# 61%*# 35%# 28%
$25,000-$74,999 43%# 40%# 25%# 31% 25%
$75,000 or more 10% 22%# 8%*# 22%# 38%
Don’t know/ refused 20%# 12% 6%# 11% 9%
Terminal degree
Less than high school 27% 14% 31% 24% 13%
High school 46%*# 33% 26%# 37% 21%
Undergraduate 27% 39%*# 25%# 20% 32%
Graduate 0% 14% 18% 19% 34%
Employment
Working full or part time 53%# 45%# 28%*# 43% 53%
Retired, disabled, unemployed 37%# 52%# 69%*# 57% 45%
Missing 10% 3% 3% 0% 2%
Study area
Somerville 67%# 38%*# 53% 69%*# 49%
Exposure variables
Workday time spent inside home (hrs) 14.6 (5.41) 17.1 (4.62) 17.4 (4.16) 16.7 (5.85) 16.8 (4.39)
Non-workday time spent inside home (hrs) 17.2 (5.37) 18.5 (4.23) 19.5 (4.12) 18.7 (5.27) 17.7 (5.20)
Previous week combustion exposure score 3.1 (2.35) 3.9 (1.92) 3.8 (2.03) 3.9 (2.38) 3.2 (1.98)
Job combustion score 3.27 (1.62) 3.21 (1.64) 3.70 (1.65) 3.20 (1.69) 3.17 (1.61)
Open windows in winter
Yes 59% 59% 63% 52% 49%
Missing 3% 3% 2% 0% 0%
Open windows in summer
Yes 96% 96% 91% 91% 94%
Missing 3% 2% 5% 0 2%
Travel on highway
Yes 17%# 4%*# 15%# 17%# 11%
Missing 3% 2% 0% 0% 0%
Health & medications
Statin medication 13% 33% 21% 33% 23%
Previous heart attack 3% 5% 9% 5% 6%
Diabetes 13% 14% 15% 15% 15%
  1. *Indicates a significant mean or proportional difference from the urban background (>1000 m).
  2. #Indicates a significant mean or proportional difference from any other group.