Table 1.
Baseline characteristics for children with lung function data at age 10 years compared with the total cohort available for the 10-year follow-up
| Characteristic | Total cohort at age 10 years | Sample with PFT data | p Value |
|---|---|---|---|
| n | 1370 | 1033 | |
| Breastfeeding duration (% (n)) | |||
| Not breast fed | 22.0 (270) | 20.5 (196) | 0.82 |
| <2 months | 25.7 (316) | 25.5 (243) | |
| 2 to <4 months | 14.7 (181) | 14.9 (142) | |
| ≥4 months | 37.5 (461) | 39.2 (374) | |
| Sex (% (n)) | |||
| Boys | 50.8 (696) | 49.8 (514) | 0.61 |
| Girls | 49.2 (674) | 50.2 (519) | |
| Maternal smoking in pregnancy* (% (n)) | |||
| ETS-0 | 45.2 (616) | 47.3 (487) | 0.43 |
| ETS-1 | 31.5 (429) | 31.5 (324) | |
| ETS-2 | 23.3 (318) | 21.3 (219) | |
| Maternal atopy (% (n)) | |||
| No | 65.8 (902) | 65.5 (677) | 0.88 |
| Yes | 34.2 (468) | 34.5 (356) | |
| Maternal asthma (% (n)) | |||
| No | 82.4 (1083) | 81.3 (799) | 0.51 |
| Yes | 17.6 (232) | 18.7 (184) | |
| Birth weight category (% (n)) | |||
| Normal | 96.3 (1284) | 96.6 (971) | 0.70 |
| Low | 3.7 (49) | 3.4 (34) | |
| Family social status cluster† | |||
| Lowest | 14.5 (188) | 13.8 (141) | 0.83 |
| Middle | 77.2 (1004) | 78.2 (801) | |
| Highest | 8.3 (109) | 8.0 (82) | |
| Maternal education (years) | |||
| Less than 16 | 10.3 (126) | 10.3 (105) | 0.82 |
| 16−18 (compulsory) | 76.4 (937) | 77.3 (786) | |
| Greater than 18 | 13.3 (163) | 12.4 (126) |
*
ETS-0, mother did not smoke during pregnancy and children not exposed to household ETS; ETS-1, mother did not smoke during pregnancy, but children were exposed to household ETS; ETS-2, mother smoked during pregnancy and children were exposed to household ETS.
†
"Family social status cluster" is a composite variable derived from a combination of family income, parental occupation (socioeconomic status) and number of children in a child's bedroom.
ETS, environmental tobacco smoke; PFT, pulmonary function test.