Characteristics of the study population by country
| Study population | Maternal age at delivery years | Maternal smoking in pregnancy | Maternal education level (primary school)# | Current asthma¶ | Respiratory symptoms+ | Atopy§ | FEV1 mL | FEV1/FVC ratio | |
| Melbourne, Australia | 615 (5.8) | 29.0 (25–33) | 104 (17.0) | 212 (57.6) | 108 (17.6) | 221 (35.9) | 225 (53.3) | 3699±834 | 79.3±6.6 |
| Belgium | 707 (6.6) | 28.6 (24–32) | 62 (8.9) | 150 (45.5) | 35 (5.0) | 116 (16.6) | 171 (31.2) | 3705±799 | 80.7±6.2 |
| Estonia | 326 (3.1) | 28.3 (24–33) | 6 (1.9) | 101 (53.7) | 6 (1.8) | 66 (20.3) | 66 (22.5) | 3788±931 | 82.9±7.5 |
| France | 1198 (11.2) | 28.8 (24–33) | 40 (3.4) | 549 (59.2) | 100 (8.4) | 207 (17.6) | 304 (33.7) | 3382±779 | 82.6±7.3 |
| Germany | 577 (5.4) | 27.4 (23–31) | 27 (4.8) | 255 (64.7) | 28 (4.9) | 89 (15.4) | 163 (30.2) | 3695±813 | 80.4±6.1 |
| Iceland | 522 (4.9) | 27.5 (22–33) | 92 (17.9) | 250 (65.3) | 41 (7.9) | 86 (16.6) | 85 (16.8) | 3427±776 | 79.6±7.3 |
| Italy | 588 (5.5) | 29.0 (25–33) | 27 (4.8) | 258 (71.3) | 33 (5.6) | 78 (13.4) | 133 (29.6) | 3457±812 | 81.4±6.3 |
| The Netherlands | 150 (1.4) | 29.8 (25–34) | 20 (13.6) | 2 (28.6) | 7 (4.7) | 26 (17.3) | |||
| Norway | 588 (5.5) | 28.7 (24–33) | 83 (14.2) | 239 (61.4) | 42 (7.2) | 115 (20.6) | 138 (25.1) | 3437±791 | 77.7±5.7 |
| Spain | 1856 (17.4) | 29.7 (25–33) | 22 (1.2) | 901 (74.7) | 147 (7.9) | 495 (26.8) | 369 (25.6) | 3364±818 | 80.1±7.0 |
| Sweden | 1832 (17.1) | 28.1 (23–32) | 286 (15.8) | 740 (64.1) | 293 (16.2) | 454 (25.4) | 413 (33.4) | 3621±798 | 80±7.1 |
| Switzerland | 549 (5.1) | 28.9 (25–33) | 23 (4.2) | 113 (63.1) | 63 (11.5) | 115 (21.2) | 200 (43.7) | 3564±870 | 78.4±7.3 |
| UK | 955 (8.9) | 27.6 (23–31) | 204 (22.0) | 246 (63.9) | 186 (19.5) | 312 (33.5) | 329 (42.7) | 3217±809 | 79±7.0 |
| Portland, USA | 229 (2.1) | 27.3 (23–31) | 61 (27.4) | 10 (34.5) | 22 (9.7) | 49 (21.9) | 67 (39.6) | 3289±705 | 78.3±5.7 |
| Total | 10 692 (100) | 28.6 (24–33) | 1057 (10.0) | 4026 (63.9) | 1111 (10.4) | 2429 (23.0) | 2663 (32.2) | 3488±825 | 80.1±7.0 |
Data are presented as n (%), median (interquartile range) or mean±sd. FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity. #: available for subsample of 6303 participants; ¶: current asthma medication and/or asthma attacks in past 12 months; +: three or more of the following symptoms in past 12 months: wheeze, wheeze with breathlessness, wheeze when not having a cold, waking with tightness in chest, shortness of breath in daytime, shortness of breath after strenuous activity, waking by shortness of breath or waking by attack of cough; §: serum IgE >0.35 kU·L−1 for Dermatophagoides pteronyssinus, cat dander, timothy grass and/or Cladosporium herbarum.