Characteristics of the cohorts defined by respiratory infection during the first year of life
| Respiratory infection in first year n=42 334 (16.7%) | No respiratory infection in first year n=211 594 (83.3%) | Total n=253 928 (100%) | |
|---|---|---|---|
| Prescribed asthma medication* | 7485 (17.7) | 26 591 (12.6) | 34 076 (13.4) |
| Hospital asthma diagnosis* | 420 (1.0) | 761 (0.4) | 1181 (0.5) |
| No asthma* | 34 749 (82.1) | 184 775 (87.3) | 219 524 (86.5) |
| Gestational age (weeks) | |||
| ≤27 | 252 (0.6) | 1221 (0.6) | 1473 (0.6) |
| 28–31 | 723 (1.7) | 3578 (1.7) | 4301 (1.7) |
| 32–36 | 3906 (9.2) | 19 528 (9.2) | 23 434 (9.2) |
| 37–41 | 34 839 (82.3) | 174 194 (82.3) | 209 033 (82.3) |
| >41 | 2507 (5.9) | 12 535 (5.9) | 15 042 (5.9) |
| Uncertain | 107 (0.3) | 538 (0.3) | 645 (0.3) |
| Birth weight (g) | |||
| <1000 | 241 (0.6) | 1292 (0.6) | 1533 (0.6) |
| >1000–1500 | 580 (1.4) | 2714 (1.3) | 3294 (1.3) |
| >1500–2000 | 953 (2.3) | 4300 (2.0) | 5253 (2.1) |
| >2000–2750 | 4099 (9.7) | 18 815 (8.9) | 22 914 (9.0) |
| >2750–3250 | 9727 (23.0) | 47 617 (22.5) | 57 344 (22.6) |
| >3250–4000 | 20 178 (47.7) | 104 693 (49.5) | 124 871 (49.2) |
| >4000 | 6426 (15.2) | 31 524 (14.9) | 37 950 (14.9) |
| Not recorded | 130 (0.3) | 639 (0.3) | 769 (0.3) |
| Maternal asthma | |||
| Current | 721 (1.7) | 2754 (1.3) | 3475 (1.4) |
| Previous | 210 (0.5) | 749 (0.4) | 959 (0.4) |
| None | 41 403 (97.8) | 208 091 (98.3) | 249 494 (98.3) |
| Maternal age at delivery | |||
| 13–18 | 755 (1.8) | 2917 (1.4) | 3672 (1.5) |
| 19–25 | 14 230 (33.6) | 66 604 (31.5) | 80 834 (31.8) |
| 26–30 | 15 312 (36.2) | 76 752 (36.3) | 92 064 (36.3) |
| 31–35 | 8911 (21.0) | 46 336 (21.9) | 55 247 (21.8) |
| 36–40 | 2757 (6.5) | 16 673 (7.9) | 19 430 (7.7) |
| 41–54 | 369 (0.9) | 2312 (1.1) | 2681 (1.1) |
| Maternal smoking | |||
| Non-smoker | 23 871 (56.4) | 134 802 (63.7) | 158 673 (62.5) |
| Smoker | 12 429 (29.4) | 46 817 (22.1) | 59 246 (23.3) |
| Not recorded | 6034 (14.3) | 29 975 (14.2) | 36 009 (14.2) |
| Child's sex | |||
| Female | 17 619 (41.6) | 103 007 (48.7) | 120 626 (47.5) |
| Male | 24 715 (58.4) | 108 587 (51.3) | 133 302 (52.5) |
| Parity | |||
| 1 | 12 714 (30.0) | 87 275 (41.2) | 99 989 (39.4) |
| 2 | 17 247 (40.7) | 74 534 (35.2) | 91 781 (36.1) |
| 3 | 8270 (19.5) | 34 880 (16.5) | 43 150 (17.0) |
| 4 or more | 4103 (9.7) | 14 905 (7.0) | 19 008 (7.5) |
| Chronic lung disease | |||
| No | 42 272 (99.9) | 211 416 (99.9) | 253 688 (99.9) |
| Yes | 62 (0.1) | 178 (0.1) | 240 (0.1) |
*These categories are not mutually exclusive.