Table 1.
Baseline characteristics of study participants in the UK Biobank
| Overall (N = 259,435) | |
|---|---|
| Age at recruitment (years) | 57 (8.01) |
| Menopausal status at recruitment | |
| Premenopausal | 77,777 (29.98%) |
| Postmenopausal | 181,658 (70.02%) |
| Body mass index (kg/m2) | |
| < 18.5 | 1957 (0.75%) |
| 18.5–25.0 | 101,021 (38.94%) |
| 25.0–30.0 | 94,871 (36.57%) |
| ≥ 30.0 | 60,662 (23.38%) |
| Number of births | |
| 0 | 48,304 (18.62%) |
| 1 | 34,532 (13.31%) |
| 2 | 113,359 (43.69%) |
| ≥ 3 | 62,625 (24.14%) |
| Family history of breast cancer | |
| No | 213,775 (82.4%) |
| Yes | 26,774 (10.32%) |
| Age at menarche (years) | |
| < 13 | 97,778 (37.69%) |
| 13–15 | 138,665 (53.45%) |
| ≥ 15 | 14,778 (5.7%) |
| Oral contraceptive use | |
| No | 48,521 (18.7%) |
| Yes | 209,742 (80.85%) |
| Hormone replacement therapy | |
| No | 159,779 (61.59%) |
| Yes | 98,337 (37.9%) |
| Smoking | |
| Never | 154,097 (59.4%) |
| Former | 80,999 (31.22%) |
| Current | 23,057 (8.89%) |