Baseline characteristics
| Total cohort (n=2443) | With 5-year follow-up (n=1007) | With 8-year follow-up (n=803) | |
| Sex male | 1191/2443 (49%) | 485/1007 (48%) | 370/803 (46%) |
| Age at follow-up in months median±sd | 65±4.6 | 107±11.6 | |
| Birth weight g | 3544±500 | 3552±498 | 3561±481 |
| wGA weeks+days | 39+6 (±9 days) | 39+6 (± 9 days) | 39+6 (± 9 days) |
| Breastfed# | 1320/2439 (54%) | 521/915 (57%) | 430/742 (42%) |
| Siblings | 1134/2443 (46%) | 421/916 (46%) | 353/743 (48%) |
| Day care attendance# | 2367/2440 (97%) | 893/915 (98%) | 723/742 (97%) |
| Pre-natal smoke exposure¶ | 318/2427 (13%) | 160/912 (18%) | 118/740 (16%) |
| Smoking parents (at least one) | 415/2008 (21%) | 173/756 (23%) | 141/632 (22%) |
| Asthmatic mother | 184/2125 (9%) | 74/808 (9%) | 62/675 (9%) |
| Asthmatic father | 116/2019 (6%) | 48/769 (6%) | 37/644 (6%) |
| Allergic mother+ | 802/2152 (37%) | 310/815 (38%) | 257/681 (38%) |
| Allergic father+ | 785/2040 (39%) | 310/774 (40%) | 262/650 (40%) |
| High educational level mother§ | 1473/2105 (70%) | 551/803 (69%) | 453/671 (68%) |
| High educational level father§ | 1284/2002 (64%) | 452/766 (59%) | 381/640 (60%) |
Data are presented as n/total (%) or mean±sd, unless otherwise stated. wGA: weeks gestational age. #: At least 1 month in the first year of life; ¶: either maternal smoking or exposure of the mother to smoke; +: reported hay fever or allergy for house-dust mite, animals or food; §: educational level higher than secondary school.