Skip to main content

Table 2 Hazard ratios (95% confidence intervals) of stroke associated with per interquartile-range increase in air pollutant, temperature and humidity

From: A cohort study evaluating the risk of stroke associated with long-term exposure to ambient fine particulate matter in Taiwan

 

1-year level at baselinea

Air pollution level as a time-varying covariated

IQR

Model 1b

Model 2 (Main model)c

Model 1b

Model 2 (Main model)c

Total Stroke

 PM2.5, μg/m3

9.6

1.07 (1.04–1.09)

1.03 (1.00–1.06)

1.07 (1.06–1.09)

1.03 (1.01–1.05)

 SO2, ppb

2.4

1.06 (1.03–1.08)

1.03 (1.00–1.05)

1.05 (1.04–1.07)

1.03 (1.02–1.05)

 NOx, ppb

14.5

0.97 (0.95–0.98)

1.04 (1.02–1.06)

0.97 (0.96–0.98)

1.04 (1.02–1.05)

 NO2, ppb

9.0

0.94 (0.92–0.96)

1.04 (1.00–1.07)

0.95 (0.93–0.96)

1.04 (1.02–1.07)

 Warm-season O3e, ppb

6.5

1.05 (1.02–1.07)

0.98 (0.96–1.00)

1.04 (1.02–1.05)

0.97 (0.96–0.99)

 CO, ppm

0.2

0.97 (0.95–0.98)

1.04 (1.02–1.06)

0.97 (0.96–0.98)

1.03 (1.01–1.04)

 Temperature, °C

1.2

1.05 (1.03–1.06)

1.02 (1.00–1.04)

1.05 (1.04–1.06)

1.02 (1.01–1.03)

 Relative humidity, %

4.1

1.01 (0.996–1.03)

1.00 (0.97–1.02)

1.00 (0.99–1.01)

0.99 (0.97–1.00)

Ischemic stroke

 PM2.5, μg/m3

9.6

1.10 (1.07–1.13)

1.06 (1.02–1.09)

1.11 (1.09–1.13)

1.05 (1.03–1.08)

 SO2, ppb

2.4

1.08 (1.05–1.10)

1.04 (1.01–1.07)

1.08 (1.06–1.10)

1.05 (1.03–1.07)

 NOx, ppb

14.5

0.96 (0.95–0.98)

1.04 (1.01–1.06)

0.97 (0.96–0.98)

1.04 (1.02–1.06)

 NO2, ppb

9.0

0.94 (0.92–0.97)

1.05 (1.01–1.09)

0.95 (0.94–0.97)

1.05 (1.03–1.08)

 Warm-season O3e, ppb

6.5

1.07 (1.05–1.10)

1.00 (0.97–1.02)

1.06 (1.04–1.08)

0.99 (0.97–1.01)

 CO, ppm

0.2

0.96 (0.95–0.98)

1.04 (1.01–1.06)

0.97 (0.96–0.98)

1.03 (1.01–1.04)

 Temperature, °C

1.2

1.06 (1.04–1.08)

1.03 (1.01–1.05)

1.06 (1.05–1.07)

1.03 (1.02–1.04)

 Relative humidity, %

4.1

1.01 (0.99–1.03)

0.99 (0.97–1.02)

0.99 (0.98–1.01)

0.98 (0.97–1.00)

Hemorrhagic stroke

 PM2.5, μg/m3

9.6

0.97 (0.92–1.01)

0.95 (0.89–1.10)

0.96 (0.93–1.00)

0.94 (0.91–0.98)

 SO2, ppb

2.4

0.98 (0.94–1.03)

0.98 (0.93–1.03)

0.97 (0.94–1.01)

0.97 (0.94–1.01)

 NOx, ppb

14.5

0.98 (0.95–1.01)

1.04 (1.00–1.08)

0.98 (0.95–1.00)

1.04 (1.00–1.07)

 NO2, ppb

9.0

0.93 (0.89–0.98)

1.02 (0.95–1.09)

0.94 (0.91–0.97)

1.01 (0.97–1.06)

 Warm-season O3e, ppb

6.5

0.97 (0.93–1.02)

0.92 (0.88–0.97)

0.97 (0.94–1.00)

0.93 (0.90–0.96)

 CO, ppm

0.2

0.98 (0.95–1.01)

1.04 (1.00–1.08)

0.98 (0.96–1.00)

1.03 (1.00–1.05)

 Temperature, °C

1.2

0.98 (0.97–1.03)

0.99 (0.96–1.02)

1.00 (0.98–1.02)

0.99 (0.96–1.01)

 Relative humidity, %

4.1

1.03 (0.99–1.07)

1.01 (0.96–1.05)

1.02 (0.99–1.04)

1.00 (0.97–1.03)

  1. Abbreviations: CO carbon monoxide, IQR interquartile range, NO2 nitrogen dioxide, NOx nitrogen oxides, O3 ozone, PM2.5 particulate matter of <2.5 μm in diameter, SO2 sulfur dioxide
  2. aThere were no missing values for the covariates in models 1 and 2. There were missing values for temperature, relative humidity and O3. Therefore, Numbers of subjects included in the analysis for each environmental exposure (single-pollutant model) were 1,323,701 for temperature and relative humidity, 1,362,284 for PM2.5, SO2, NOx, NO2 and CO, and 1,344,570 for O3
  3. bModel 1 was adjusted for age and sex
  4. cModel 2 was adjusted for age, sex, income, and urbanization level
  5. dObervations with missing values were excluded from the time-vary Cox proportional hazard models. Numbers of observations included in the models were: 7,569,935 for temperature and relative humidity, 7, 797,277 for PM2.5, SO2, NOx, NO2; 7,637,106 for O3; and 7,791,276 for CO.
  6. eApril-October daily maximum 8-h ozone concentrations
Back to article page

Environmental Health

ISSN: 1476-069X