Population characteristics for the two study populations
| Characteristic | Cross-sectional analyses population# | Longitudinal analyses population# | ||||
| Total | Boys | Girls | Total | Boys | Girls | |
| Subjects n | 721 | 338 | 383 | 915 | 434 | 481 |
| Parental atopy | ||||||
| Atopic mother | 232 (32.1) | 111 (32.8) | 121 (31.5) | 434 (47.4) | 211 (48.6) | 223 (46.3) |
| Atopic father | 242 (33.6) | 114 (33.7) | 128 (33.5) | 306 (33.5) | 144 (33.1) | 162 (33.7) |
| Boys | 338 (46.8) | 434 (47.4) | ||||
| Presence of pets at 3 months | 302 (41.8) | 134 (39.4) | 168 (43.8) | 409 (44.9) | 182 (41.9) | 212 (44.0) |
| Presence of moulds at 3 months | 193 (27.2) | 112 (36.6) | 144 (41.5) | 243 (27.1) | 143 (36.4) | 169 (38.9) |
| Breastfeeding more than 12 weeks | 434 (60.2) | 191 (56.5) | 243 (63.4) | 534 (58.4) | 246 (56.6) | 288 (59.8) |
| Gas cooking at 3 months | 613 (85.3) | 281 (83.1) | 332 (87.3) | 771 (84.7) | 355 (82.2) | 416 (87.0) |
| Maternal smoking during pregnancy | 92 (12.8) | 38 (11.3) | 54 (14.1) | 124 (13.6) | 54 (12.5) | 70 (14.6) |
| Indoor tobacco smoke exposure at 3 months | 146 (20.2) | 69 (20.4) | 77 (20.1) | 192 (20.9) | 89 (20.5) | 103 (21.4) |
| Parental education | ||||||
| Low | 53 (7.3) | 27 (7.9) | 26 (6.7) | 75 (8.2) | 40 (9.2) | 35 (7.3) |
| Intermediate | 215 (29.8) | 97 (28.7) | 118 (30.8) | 282 (30.8) | 127 (29.2) | 155 (32.3) |
| High | 453 (62.8) | 214 (63.3) | 239 (62.4) | 557 (60.9) | 267(61.5) | 290 (60.4) |
| Dutch nationality | 686 (97.1) | 323 (97.3) | 363 (96.8) | 872 (96.5) | 413 (96.0) | 459 (96.9) |
| Asthma at age 16 | 59 (8.5) | 32 (9.8) | 27 (7.3) | 55 (9.1) | 29 (10.2) | 26 (8.0) |
| Respiratory infections¶ | ||||||
| Age 16 | 303 (42.1) | 128 (37.8) | 175 (45.7) | 266 (42.1) | 111 (38.1) | 155 (45.3) |
| Age 12 | 298 (33.7) | 121 (28.8) | 177 (38.1) | |||
| Age 8 | 102 (5.3) | 65 (21.5) | 95 (28.8) | |||
Data is presented as n (%), unless otherwise stated. #: the value of n is smaller than indicated for some variables due to missing data; ¶: respiratory infections in the 3 weeks before lung function measurement.