Table 2

Sample characteristics by cohort

VariablesGenR
Netherlands
n=4277
LSAC B
Australia
n=3759
ABIS
Sweden
n=4026
MCS
UK
n=13 354
QLSCD
Quebec
n=1334
NLSCY
Canada
n=1356
US NLSY
USA
n=3104*
Asthma (ever)Yes357 (8.3)1095 (29.1)528 (13.1)2401 (18.0)302 (22.6)234 (17.3)491 (15.8)
(n, %)No3537 (82.7)2664 (70.9)3498 (86.9)10 951 (82.0)1032 (77.4)1073 (79.1)2613 (84.2)
Missing383 (9.0)0 (0)0 (0)2 (0)0 (0)49 (3.6)0 (0)
Wheezing or asthma attack (past year)Yes178 (4.2)387 (10.3)424 (10.5)1590 (11.9)52 (3.9)183 (13.5)227 (16.8)
(n, %)No3818 (89.3)3304 (87.9)3602 (89.5)11 762 (88.1)1282 (96.1)123 (82.8)1126 (83.2)
Missing281 (6.6)68 (1.8)0 (0)2 (0.0)0 (0)50 (3.7)0 (0)*
Medication control (past year)Yes186 (4.3)n/a176 (4.4)610 (4.6)157 (11.8)94 (7.0)84 (6.2)
(n, %)No3430 (80.2)n/a3840 (95.4)12 744 (95.4)1177 (88.2)1213 (89.0)1269 (93.8)
Missing661 (15.5)3759 (100)10 (0.2)0 (0)0 (0)49 (4.0)0 (0)*
Household incomeHigh (Q5)683 (16.0)831 (22.1)985 (24.5)2299 (17.2)286 (21.4)365 (26.9)570 (18.4)
(n, %; by quintile groups)Middle (Q2–4)2823 (66.0)2352 (62.6)2468 (61.3)7714 (57.8)782 (58.6)874 (64.5)1581 (50.9)
Low (Q1)771 (18.0)576 (15.3)569 (14.1)2829 (21.2)210 (15.7)117 (8.6)731 (23.6)
Missing0 (0)0 (0)4 (0.1)512 (3.8)56 (4.2)0 (0)222 (7.2)
Maternal educationalHigh2440 (57.0)1796 (47.8)1705 (42.8)4175 (31.3)463 (34.7)567 (41.8)902 (29.1)
(n, %; by three categories)Middle1224 (28.6)1624 (43.2)2107 (52.9)5545 (41.5)536 (40.2)568 (41.9)1670 (53.9)
Low613 (14.3)337 (9.0)174 (4.4)3135 (23.5)335 (25.1)187 (13.8)528 (17.0)
Missing0 (0)2 (0.05)40 (1.0)499 (3.7)0 (0)34 (2.5)4 (0.1)
Child age (mean, SD)Years9.7 (0.3)10.9 (0.01)10.6 (0.3)10.7 (0.5)10.1 (0.3)10.1 (0.3)10.5 (0.7)
Child sexMale2120 (49.6)1928 (51.3)2044 (50.8)6730 (50.4)635 (47.6)687 (50.7)1599 (51.5)
(n, %)Female2157 (50.4)1831 (48.7)1982 (49.2)6624 (49.6)699 (52.4)669 (49.3)1505 (48.5)
Missing0 (0)0 (0)0 (0)0 (0)0 (0)0 (0)0 (0)
Mother ethnicityEthnic majority/born in country2873 (67.2)2453 (65.3)3790 (94.1)10 747 (80.5)1224 (91.8)1196 (88.0)1627 (52.4)
(n, %)Ethnic minority/born out country1404 (32.8)1297 (34.5)195 (4.8)2104 (15.8)109 (8.2)116 (9.0)1477 (47.6)
Missing0 (0)9 (0.2)41 (1.0)503 (3.8)1 (0.1)44 (3.0)0 (0)
Maternal age at birth†<25 years383 (9.0)436 (11.6)400 (9.9)3158 (23.7)310 (23.2)310 (22.9)113 (3.6)
(n, %)25–29 years1020 (23.8)986 (26.3)1594 (39.6)3577 (26.8)420 (31.5)451 (33.3)1364 (43.9)
30–34 years1976 (46.2)1490 (39.6)1407 (34.9)4502 (33.7)446 (33.4)435 (32.1)1411 (45.5)
≥35 years898 (21.0)844 (22.5)596 (14.8)1638 (12.3)157 (11.8)145 (10.7)216 (7.0)
Missing0 (0)3 (0.1)29 (0.7)478 (3.6)1 (0.1)15 (1.1)0 (0)
  • Sample size may differ from baseline N reported in online supplemental table 1 due to missing data for SES exposure in early childhood or asthma in late childhood or cohort attrition.

  • *USNLSY included detailed questions about wheezing and asthma medications starting in 2004; subsample (n=1353) restricted to children born 1992 or later was used for these two variables.

  • †Mother age at child birth categories differed for NLSCY (Canada): 15–24, 25–29, 30–34, 35+, missing.

  • ABIS, All Babies in Southeast Sweden; LSAC, Longitudinal Study of Australian Children B-Cohort; MCS, Millennium Cohort Study; NLSCY, National Longitudinal Survey of Children and Youth; QLSCD, Québec Longitudinal Study of Child Development; SES, socioeconomic status; USNLSY, US National Longitudinal Survey of Youth, Children and Young Adults.