Table 1 Descriptive data on educational status of the study population
From: Does lower educational attainment increase the risk of osteoarthritis surgery? a Swedish twin study
Whole study sample | DZ and MZ complete and incomplete twin pairs | DZ complete twin pairs | MZ complete twin pairs | Â | |||
|---|---|---|---|---|---|---|---|
| Â | Years of education, continuous | Â | |||||
Years of education, mean years ± SD | 11.2 ± 2.9 | 11.1 ± 2.9 | 11.5 ± 2.9 |  | |||
| Â | Years of education, categorical | Â | |||||
|  |  < 13 |  ≥ 13 |  < 13 |  ≥ 13 |  < 13 |  ≥ 13 | Missing |
Number of people, n | 47,753 | 19,318 | 27,365 | 10,203 | 11,703 | 5,611 | 1,077 |
Sex, Females, % missing, % | 53.0 0.0 | 55.6 0.0 | 52.0 0.0 | 53.3 0.0 | 54.7 0.0 | 58.4 0.0 | 5.1 86.7 |
Age at entry, mean age ± SD | 42.9 ± 9.1 | 38.6 ± 6.5 | 43.2 ± 9.0 | 39.2 ± 6.8 | 42.3 ± 8.9 | 38.1 ± 6.0 | 44.0 ± 10.9 |
Knee OA surgery, n | 1,681 | 336 | 1,009 | 216 | 399 | 75 | 10 |
Hip OA surgery, n | 1,800 | 485 | 1,065 | 277 | 421 | 135 | 9 |
Person-years follow-up, knee OA surgery | 1,132,628 | 383,220 | 676,037 | 220,142 | 271,134 | 102,707 | 6,592 |
Person-years follow-up, hip OA surgery | 1,130,901 | 381,587 | 675,129 | 219,273 | 270,593 | 102,108 | 6,588 |