Table 1

Descriptive characteristics of the overall study cohort and incident cohort

Overall cohort
(n=2 051 403)
Incident cohort
(n=12 277)
Median age at entry, years (IQR)5.5 (0.8–11.5)7.6 (3.5–10.5)
Follow-up time, years (IQR)3.5 (1.5–6.3)4.2 (2–6.1)
Sex, n (%)
 Male1 055 395 (51.5)4936 (40.2)
 Female996 008 (48.6)7341 (59.8)
Ethnicity, n (%)
 White878 360 (42.8)2836 (23.1)
 Asian/Asian British76 840 (3.8)2928 (23.9)
 Black/African/Caribbean/Black British47 206 (2.3)1275 (10.4)
 Other ethnic group17 656 (0.9)312 (2.5)
 Mixed/multiple ethnic group28 605 (1.4)295 (2.4)
 Missing1 002 736 (48.9)4631 (37.7)
Country of GP practice, n (%)
 England1 451 923 (70.8)10 921 (88.9)
 Northern Ireland84 171 (4.1)177 (1.4)
 Scotland310 142 (15.1)597 (4.9)
 Wales205 167 (10)582 (4.7)
Townsend deprivation index quintile, n (%)
 1 (least deprived)397 057 (19.4)1452 (11.8)
 2357 567 (17.4)1377 (11.2)
 3396 234 (19.3)2128 (17.3)
 4379 485 (18.5)2740 (22.3)
 5 (most deprived)291 502 (14.2)2866 (23.3)
 Missing229 558 (11.2)1714 (14)
Year of cohort entry, n (%)
 20081 060 098 (51.7%)6831 (55.6%)
 2009130 610 (6.4%)954 (7.8%)
 2010126 825 (6.2%)961 (7.8%)
 2011160 853 (7.8%)1020 (8.3%)
 2012134 390 (6.6%)870 (7.1%)
 2013139 113 (6.8%)757 (6.2%)
 2014119 354 (5.8%)503 (4.1%)
 201597 198 (4.7%)279 (2.3%)
 201682 962 (4.0%)102 (0.8%)
  • Children with no recorded data on ethnicity or Townsend index were categorised as ‘missing’.

  • IQR, IQR range.