Table 3

Sample characteristics by cohort (unweighted frequencies)

VariablesMCSABISLSAC KGenRNLSCYUSNLSY
UKSwedenAustraliaNetherlandsCanadaUSA
(n=13 354)(n=16 365)(n=4164)(n=8305)(n=1356)(n=3657)
Child sex (n, %)Male6589 (50.0)8485 (51.9)2034 (48.8)4188 (50.4)687 (51)1881 (51.4)
Female6601 (50.0)7880 (48.1)2130 (51.2)4117 (49.6)669 (49)1776 (48.6)
Mother age at child birth*
(n, %)
<20925 (6.9)218 (1.3)91 (2.2)274 (3.3)310 (22.9)0
20–295809 (43.5)8722 (53.7)1763 (42.3)3339 (40.2)451 (33.2)1767 (48.3)
30–395849 (43.8)6996 (43.1)2144 (51.5)4503 (54.2)435 (32.1)1887 (51.6)
40+293 (2.2)307 (1.9)140 (3.4)186 (2.2)144 (10.6)0
Missing478 (3.6)122 (0.01)26 (0.6)3 (0.1)16 (1.2)3 (0.1)
Mother ethnicityTerminologyMajority/minorityMajority/minorityBorn in country/born outsideMajority/minorityBorn in country/born outsideMajority/minority
Ethnic majority/born in country10 919 (81.8)14 960 (91.4)2632 (63.2)4234 (51.0%)1232 (91.0%)2050 (56.1%)
Ethnic minority/born outside country1623 (14.4)1062 (6.6)1500 (36.0)3722 (44.8)123 (9.0)1607 (43.9%)
Missing504 (3.8)343 (2.0)32 (0.8)349 (4.2)1 (0)0
Multiple births (n, %)Yes343 (2.6)380 (2.3)114 (2.7)208 (2.5)36 (3.0)91 (2.5)
No12 534 (93.9)15 985 (97.7)4049 (97.2%)8097 (97.5)1283 (95.0)3566 (97.5)
Missing477 (3.6)01 (0.0)0 (0)37 (3.0)0
Outcome: ALCHC by late childhood (n, %)Yes1011 (7.6)943 (5.8)194 (4.7)980 (11.8)170 (13.0)220 (6.0)
No12 343 (92.4)15 451 (94.2)3970 (95.3)4283 (51.6)1137 (84.0)2869 (78.5)
Missing0 (0)0 (0)0 (0)3042 (36.6)49 (4.0)568 (15.5)
Child age at ALCHC assessment†‡§ (mean, SD)Years11.2 (0.48)11.0 (na§)10.3 (0.50)6.18 (0.49)10.8 (0.30)10.5 (0.74)
Exposure: income in early childhood
(n, %; by quintile)
Q1 (richest)2299 (17.2)3259 (19.9)903 (21.7)1340 (16.1)365 (26.9)570 (15.6)
Q22483 (18.6)3251 (19.9)889 (21.3)682 (8.2)396 (29.2)570 (15.6)
Q32483 (18.6)3250 (19.9)849 (20.4)1581 (19.0)219 (16.1)559 (15.3)
Q42748 (20.6)3251 (19.9)806 (19.4)904 (10.9)259 (19.1)452 (12.4)
Q5 (poorest)2829 (21.2)3242 (19.8)717 (17.2)1386 (16.7)117 (8.6)825 (22.6)
Missing512 (3.8)112 (0.7)0 (0)2412 (29.0)0 (0)681 (18.6)
Exposure:
Maternal education at baseline (n, %; by three categories)
High4176 (31.3)5068 (31.0)1287 (30.9)3374 (40.6)567 (42.0)1073 (29.3)
Middle5544 (41.5)9525 (58.2)2296 (55.1)2257 (27.2)568 (42.0)1922 (52.6)
Low2782 (20.8)1379 (8.4)555 (13.3)1832 (22.1)187 (14.0)657 (18.0)
Missing852 (6.4)393 (2.4)26 (0.6)842 (10.1)34 (3.0)5 (0.1)
  • *Mother age at child birth categories differed for NLSCY (Canada): 15–24, 25–29, 30–34, 35+, Missing. Sample size may differ from baseline N reported in table 1 due to missing data for SES exposure in early childhood or ALCHC in late childhood, or cohort attrition.

  • †ALCHC measured at age 10–11 years in LSAC K.

  • ‡ALCHC measured at age 6 years in GenR.

  • §SD not measurable in ABIS as diagnoses made at >11 years were excluded.

  • ABIS, All Babies in South-East Sweden; ALCHC, activity-limiting chronic health conditions; GenR, Generation R; LSAC K, Longitudinal Study of Australian Children K-cohort; MCS, Millennium Cohort Study; NLSCY, National Longitudinal Study of Children and Youth; SES, socioeconomic status; USNLSY, National Longitudinal Survey of Youth Children and Young Adults.