Characteristic | Cases n=8127 | Controls n=40 136 |
Sex, n (%) | ||
Male | 6716 (82.6) | 33 164 (82.6) |
Age group at diagnosis (years), n (%) | ||
4 | 176 (2.2) | 1013 (2.5) |
5–6 | 1445 (17.8) | 7092 (17.7) |
7–10 | 3661 (45.1) | 17 943 (44.7) |
11–17 | 2845 (35.0) | 14 088 (35.1) |
Period of start of study, n (%) | ||
1998–1999 | 2137 (26.3) | 11 185 (27.9) |
2000–2004 | 3548 (43.6) | 17 373 (43.3) |
2005–2009 | 2062 (25.4) | 9965 (24.8) |
2010–2015 | 380 (4.7) | 1613 (4.0) |
Deprivation quintile, n (%) | ||
1st quintile (least deprived) | 1355 (16.7) | 8879 (22.1) |
2nd quintile | 1366 (16.8) | 7818 (19.5) |
3rd quintile | 1527 (18.8) | 7769 (19.4) |
4th quintile | 1751 (21.6) | 7602 (18.9) |
5th quintile (most deprived) | 2120 (26.1) | 8020 (20.0) |
Data missing | 8 (0.1) | 48 (0.1) |
Region, n (%) | ||
North East | 193 (2.4) | 958 (2.4) |
North West | 1118 (13.8) | 5517 (13.8) |
Yorkshire & The Humber | 164 (2.0) | 813 (2.0) |
East Midlands | 263 (3.2) | 1289 (3.2) |
West Midlands | 763 (9.4) | 3757 (9.4) |
East of England | 1180 (14.5) | 5789 (14.4) |
South West | 787 (9.7) | 3887 (9.7) |
South Central | 1206 (14.8) | 5974 (14.9) |
London | 871 (10.7) | 4297 (10.7) |
South East Coast | 1582 (19.5) | 7855 (19.6) |
Sex, age and practice were matching variables. Therefore, cases and controls were registered at the same GP practice.
ADHD, attention-deficit/hyperactivity disorder ; GP, general practitioner.