Association between exposure to nitrogen dioxide (NO2) and first asthma hospital admission after baseline (1993–1997) in the Diet, Cancer and Health cohort
| Population | NO2 (IQR 5.8 μg/m3) | Adjusted for age | Adjusted for age and smoking* | Fully adjusted† |
| HR (95%CI) | HR (95% CI) | HR (95% CI) | ||
| Full cohort, n=53 695 | Linear trend | 1.15 (1.06 to 1.24) | 1.14 (1.05 to 1.23) | 1.12 (1.04 to 1.22) |
| <13.4 μg/m3 | 1.00 | 1.00 | 1.00 | |
| 13.4–15.2 μg/m3 | 1.30 (1.08 to 1.58) | 1.29 (1.07 to 1.56) | 1.28 (1.05 to 1.54) | |
| 15.2–19.2 μg/m3 | 1.23 (1.02 to 1.50) | 1.21 (1.00 to 1.47) | 1.20 (0.99 to 1.46) | |
| ≥19.2 μg/m3 | 1.43 (1.19 to 1.72) | 1.41 (1.17 to 1.69) | 1.38 (1.14 to 1.66) | |
| No asthma hospitalisation before baseline, n=53 143 | Linear trend | 1.13 (1.03 to 1.23) | 1.12 (1.02 to 1.22) | 1.10 (1.01 to 1.20) |
| <13.4 μg/m3 | 1.00 | 1.00 | 1.00 | |
| 13.4–15.2 μg/m3 | 1.23 (1.00 to 1.51) | 1.22 (0.99 to 1.50) | 1.20 (0.97 to 1.48) | |
| 15.2–19.2 μg/m3 | 1.18 (0.95 to 1.45) | 1.16 (0.94 to 1.43) | 1.14 (0.93 to 1.41) | |
| ≥19.2 μg/m3 | 1.36 (1.11 to 1.66) | 1.33 (1.09 to 1.63) | 1.30 (1.06 to 1.59) | |
| History of asthma hospitalisation before baseline, n=552 | Linear trend | 1.40 (1.15 to 1.70) | 1.39 (1.13 to 1.67) | 1.41 (1.15 to 1.71) |
| <13.4 μg/m3 | 1.00 | 1.00 | 1.00 | |
| 13.4–15.2 μg/m3 | 1.35 (0.83 to 2.18) | 1.35 (0.83 to 2.19) | 1.28 (0.79 to 2.07) | |
| 15.2–19.2 μg/m3 | 1.41 (0.86 to 2.31) | 1.38 (0.84 to 2.26) | 1.32 (0.80 to 2.18) | |
| ≥19.2 μg/m3 | 1.90 (1.19 to 3.05) | 1.84 (1.15 to 2.96) | 1.87 (1.16 to 3.02) |
IQR, difference between 25th and 75th percentiles.
↵* Smoking status (never, previous, current), smoking intensity, smoking duration and environmental tobacco smoke.
↵† Smoking status (never, previous, current), smoking intensity, smoking duration, environmental tobacco smoke, occupational exposures, gender, body mass index and educational level.