Number of older siblings and incidence of asthma in the two different periods of person-year time
| No of older siblings | Asthma at any time |
Asthma diagnosed at <2.1 years | Asthma diagnosed at >2.1 years | |||||
| HR | 95% CI | HR | 95% CI | HR | 95% CI | |||
| 0 | 1.00 | 1.00 | 1.00 | |||||
| 1 | 1.13 | 1.06 to 1.20 | 1.30 | 1.21 to 1.40 | 0.90 | 0.80 to 1.01 | ||
| 2 | 1.18 | 1.09 to 1.27 | 1.42 | 1.30 to 1.55 | 0.78 | 0.67 to 0.92 | ||
| >3 | 1.17 | 1.06 to 1.28 | 1.38 | 1.24 to 1.54 | 0.66 | 0.52 to 0.82 | ||