Analysis of age at first exposure to an influenza season and the intensity of that season in a study of leukemia risk among California children diagnosed between 1997 and 2007
| Low-intensity influenza season | Medium-intensity influenza season | High-intensity influenza season | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Controls | Cases | OR (95% CI) | Controls | Cases | OR (95% CI) | Controls | Cases | OR (95% CI) | |
| Age at first exposure to influenza season, mo | |||||||||
| 0–3 | 2,923 | 139 | Ref | 3,689 | 164 | Ref | 3,180 | 152 | Ref |
| 3–6 | 2,140 | 109 | 1.07 (0.83–1.39) | 3,066 | 150 | 1.10 (0.88–1.38) | 2,812 | 157 | 1.17 (0.93–1.47) |
| 6–9 | 1,990 | 99 | 1.05 (0.80–1.36) | 2,904 | 158 | 1.22 (0.98–1.53) | 2,649 | 123 | 0.97 (0.76–1.24) |
| 9–12 | 2,010 | 101 | 1.06 (0.81–1.37) | 1,977 | 117 | 1.33 (1.04–1.70) | 837 | 49 | 1.23 (0.88–1.71) |
| >12 | 189 | 9 | 1.00 (0.50–2.00) | 474 | 19 | 0.90 (0.56–1.46) | 0 | 0 | |
| First births | |||||||||
| Age at first exposure to influenza season, mo | |||||||||
| 0–3 | 1,122 | 48 | Ref | 1,409 | 54 | Ref | 1,283 | 61 | Ref |
| 3–6 | 859 | 38 | 1.03 (0.67–1.60) | 1,195 | 53 | 1.16 (0.79–1.70) | 1,097 | 62 | 1.19 (0.83–1.71) |
| 6–9 | 743 | 35 | 1.10 (0.71–1.72) | 1,118 | 53 | 1.24 (0.84–1.82) | 1,035 | 42 | 0.85 (0.57–1.28) |
| 9–12 | 766 | 37 | 1.13 (0.73–1.75) | 762 | 52 | 1.78 (1.21–2.63) | 313 | 24 | 1.61 (0.99–2.63) |
| >12 | 88 | 2 | 190 | 9 | 1.24 (0.60–2.54) | 0 | 0 | ||
| Second or subsequent births | |||||||||
| Age at first exposure to influenza season, mo | |||||||||
| 0–3 | 1,799 | 91 | Ref | 2,280 | 110 | Ref | 1,894 | 91 | Ref |
| 3–6 | 1,280 | 71 | 1.10 (0.80–1.51) | 1,871 | 97 | 1.08 (0.81–1.42) | 1,713 | 95 | 1.15 (0.86–1.55) |
| 6–9 | 1,247 | 64 | 1.02 (0.73–1.41) | 1,786 | 105 | 1.22 (0.93–1.60) | 1,612 | 81 | 1.05 (0.77–1.42) |
| 9–12 | 1,243 | 64 | 1.02 (0.73–1.41) | 1,215 | 65 | 1.11 (0.81–1.52) | 524 | 25 | 0.99 (0.63–1.56) |
| >12 | 101 | 7 | 1.37 (0.62–3.03) | 284 | 10 | 0.73 (0.38–1.41) | 0 | 0 | |