Table 1. Characteristics of the study population with complete data on wheezing from birth to 81 months (n = 6265) compared with those with missing data.
| Children with complete data on wheezing (n = 6265) | Children with 2–6 observations (n = 5413) | Children with 0–1 observations (n = 2384) | ||||
| n/total | % | n/total | % | n/total | % | |
| Girls | 3029/6265 | 48 | 2623/5413 | 48 | 1138/2382 | 48 |
| Demographic data | ||||||
| Rented house | 973/6143 | 16 | 1583/5116 | 31 | 943/1483 | 51 |
| Mother not married | 1041/6202 | 17 | 1427/5154 | 28 | 758/1864 | 41 |
| Overcrowding | 218/6088 | 4 | 404/5019 | 8 | 260/1771 | 15 |
| One or more siblings | 3289/6125 | 54 | 2862/5069 | 56 | 1043/1813 | 58 |
| Low maternal education* | 3496/6183 | 57 | 3531/4975 | 71 | 1038/1309 | 79 |
| Teenage mother | 89/6265 | 1 | 303/5413 | 6 | 263/2384 | 11 |
| Mother manual occupation | 793/5380 | 15 | 933/3851 | 24 | 284/868 | 33 |
| Partner manual occupation | 2158/5728 | 38 | 2112/4285 | 49 | 583/985 | 59 |
| Prevalence of wheeze | ||||||
| At 6 months | 1506/6265 | 24 | 1338/4644 | 29 | 165/507 | 33 |
| 6 months | 1506/6265 | 24 | 1338/4644 | 29 | 165/507 | 33 |
| 18 months | 1645/6265 | 26 | 1334/4574 | 29 | 43/138 | 31 |
| 30 months | 1336/6265 | 21 | 905/3671 | 25 | 21/54 | 39 |
| 42 months | 1051/6265 | 17 | 705/3705 | 19 | 5/34 | 15 |
| 54 months | 1128/6265 | 18 | 644/3122 | 21 | 7/23 | 30 |
| 69 months | 938/6265 | 15 | 389/2327 | 17 | 1/9 | 11 |
| 81 months | 852/6265 | 14 | 273/2127 | 13 | 4/11 | 36 |
*Low maternal education classified as “O” level or below (equivalent to school leaving certificate at 16 years in the UK).