Distribution of covariables in three British birth cohorts
| 1946 cohort | 1958 cohort | 1970 cohort | ||||
| Whole cohort (n=2894) | Long-term sick leave (n=159) | Whole cohort (n=15 053) | Long-term sick leave (n=431) | Whole cohort (n=14 713) | Long-term sick leave (n=153) | |
| Sex | ||||||
| Male | 1561 (54%) | 72 (45%) | 7483 (50%) | 190 (44%) | 7373 (50%) | 62 (41%) |
| Female | 1333 (46%) | 89 (55%) | 7570 (50%) | 241 (55%) | 7340 (50%) | 91 (59%) |
| Social class at birth | ||||||
| I/II | 656 (23%) | 18 (11%) | 2611 (17%) | 37 (8%) | 2431 (17%) | 20 (13%) |
| III | 1505 (52%) | 76 (47%) | 8849 (59%) | 274 (64%) | 10 359 (70%) | 80 (52%) |
| IV/V | 733 (25%) | 67 (42%) | 3593 (24%) | 120 (28%) | 1923 (13%) | 53 (35%) |
| Educational attainment | ||||||
| Degree | 30 (1%) | 1 (0.5%) | 1867 (12%) | 21 (5%) | 2708 (18%) | 16 (10%) |
| A levels | 270 (9%) | 3 (2%) | 1962 (13%) | 86 (20%) | 2054 (14%) | 14 (9%) |
| O levels | 740 (26%) | 17 (10.5%) | 5200 (35%) | 143 (33%) | 6178 (42%) | 77 (50%) |
| CSEs | 575 (20%) | 25 (16%) | 4204 (28%) | 79 (18%) | 2904 (20%) | 34 (22%) |
| No qualifications | 1279 (44%) | 115 (71%) | 1820 (12%) | 103 (24%) | 869 (6%) | 12 (8%) |
| Social class at last sweep | ||||||
| I/II | 1284 (45%) | 40 (25%) | 2675 (18%) | 55 (13%) | 6037 (41%) | 47 (31%) |
| III | 1138 (39%) | 60 (37%) | 7779 (52%) | 220 (51%) | 6159 (42%) | 64 (42%) |
| IV/V | 472 (16%) | 61 (38%) | 4599 (30%) | 156 (36%) | 2517 (17%) | 42 (27%) |
| Previous depression | ||||||
| Yes | 502 (17%) | 37 (23%) | 946 (6%) | 73 (17%) | 3387 (23%) | 36 (24%) |
| No | 2392 (83%) | 124 (77%) | 14 107 (94%) | 358 (83%) | 11 326 (77%) | 117 (76%) |
| Cognitive ability in childhood | ||||||
| Quartile 1 (least able) | 657 (23%) | 76 (47%) | 3768 (25%) | 175 (41%) | 3663 (25%) | 49 (32%) |
| Quartile 2 | 707 (24%) | 37 (23%) | 3776 (25%) | 125 (29%) | 3758 (26%) | 47 (31%) |
| Quartile 3 | 757 (26%) | 28 (17%) | 3907 (26%) | 77 (18%) | 3722 (25%) | 35 (23%) |
| Quartile 4 (most able) | 773 (27%) | 20 (13%) | 3602 (24%) | 54 (12%) | 3570 (24%) | 22 (14%) |