Table 2.
Stroke incidence associated with long term exposure to fine particulate matter (PM2.5)*. Values are hazard ratios (95% confidence intervals) unless stated otherwise
| Characteristics | Quarters of PM2.5 levels | P trend | PM2.5 per 10 µg/m3 increment | |||
|---|---|---|---|---|---|---|
| First (31.2-54.5 μg/m3) | Second (54.6-59.6 μg/m3) | Third (59.7-78.2 μg/m3) | Fourth (78.3-97.0 μg/m3) | |||
| Stroke incidence | ||||||
| Person years | 270 110 | 212 760 | 216 536 | 200 808 | — | — |
| No of cases | 825 | 718 | 995 | 1002 | — | — |
| Incidence rate† | 305.4 | 337.5 | 459.5 | 499.0 | — | — |
| Model 1‡ | 1.00 | 1.06 (0.95 to 1.17) | 1.80 (1.63 to 1.98) | 2.02 (1.83 to 2.22) | <0.001 | 1.26 (1.23 to 1.29) |
| Model 2§ | 1.00 | 1.20 (1.06 to 1.35) | 1.54 (1.34 to 1.76) | 1.95 (1.72 to 2.22) | <0.001 | 1.22 (1.18 to 1.27) |
| Model 3¶ | 1.00 | 1.11 (0.98 to 1.26) | 1.30 (1.13 to 1.49) | 1.53 (1.34 to 1.74) | <0.001 | 1.13 (1.09 to 1.17) |
| Ischemic stroke | ||||||
| Person years | 270 799 | 213 025 | 217 093 | 201 306 | — | — |
| No of cases | 495 | 435 | 627 | 719 | — | — |
| Incidence rate† | 182.8 | 204.2 | 288.8 | 357.2 | — | — |
| Model 1‡ | 1.00 | 1.10 (0.97 to 1.26) | 2.09 (1.85 to 2.37) | 2.62 (2.32 to 2.95) | <0.001 | 1.35 (1.31 to 1.39) |
| Model 2§ | 1.00 | 1.18 (1.01 to 1.38) | 1.77 (1.49 to 2.11) | 2.31 (1.97 to 2.71) | <0.001 | 1.29 (1.24 to 1.35) |
| Model 3¶ | 1.00 | 1.10 (0.94 to 1.29) | 1.49 (1.25 to 1.77) | 1.82 (1.55 to 2.14) | <0.001 | 1.20 (1.15 to 1.25) |
| Hemorrhagic stroke | ||||||
| Person years | 271 437 | 213 425 | 218 300 | 203 168 | — | — |
| No of cases | 264 | 216 | 290 | 249 | — | — |
| Incidence rate† | 97.3 | 101.2 | 132.8 | 122.6 | — | — |
| Model 1‡ | 1.00 | 0.97 (0.81 to 1.18) | 1.41 (1.19 to 1.68) | 1.39 (1.16 to 1.66) | <0.001 | 1.14 (1.09 to 1.19) |
| Model 2§ | 1.00 | 1.31 (1.04 to 1.66) | 1.64 (1.27 to 2.12) | 1.99 (1.56 to 2.55) | <0.001 | 1.23 (1.15 to 1.31) |
| Model 3¶ | 1.00 | 1.21 (0.94 to 1.54) | 1.40 (1.07 to 1.82) | 1.50 (1.16 to 1.93) | <0.001 | 1.12 (1.05 to 1.20) |
*
Particles of diameter ≤2.5 μm.
†
Incident rate per 100 000 person years.
‡
Model 1: stratified Cox proportional hazard model, adjusted for age and sex.
§
Model 2: model 1+adjusted for geographic region and urbanization.
¶
Model 3: Model 2+adjusted for education, smoking status, alcohol consumption, physical activity, body mass index, and hypertension.