Odds ratios with 95% confidence intervals for hospital admission for asthma by traffic volume within 150 m of place of residence
| Volume within 150 m | Unadjusted | Adjusted for age, sex, hospital and deprivation |
| <1500 | 1.0 | 1.0 |
| 1500–14 999 | 1.06 (0.90 to 1.24) | 1.03 (0.87 to 1.22) |
| 15 000–49 999 | 0.86 (0.73 to 1.00) | 0.80 (0.68 to 0.95) |
| 50 000+ | 0.93 (0.79 to 1.11) | 0.88 (0.74 to 1.06) |
| Statistical tests: | ||
| Heterogeneity (3 df) | χ2= 6.83; p = 0.08 | χ2 = 10.4; p = 0.02 |
| Trend (1 df) | χ2 = 2.38; p = 0.12 | χ2 = 3.58; p = 0.06 |