Table 1.
Characteristics of the Women’s Health Initiative and UK Biobank participants included in observational and one-sample instrumental variable (IV) analysis
| Women's Health Initiative |
UK Biobank |
||
|---|---|---|---|
| Observational analysis (n = 106 853) | IV analysis (n = 19 543) | Observational and IV analysis (n = 95 464) | |
| Quantitative variables | Mean (SD) or median (first, third quartile) | ||
| Main exposure | |||
| ANM (years) | 49.1 (5.9) | 49.3 (5.9) | 50.3 (4.5) |
| Other | |||
| Age (years) | 63.6 (7.2) | 65.7 (6.9) | 60.6 (5.4) |
| BMI (kg/m2) | 27.5 (5.7) | 27.9 (5.7) | 27 (5.0) |
| Systolic BP (mmHg) | 128.6 (19.2) | 131 (19.5) | 140.5 (20.3) |
| Townsend index | –1.7 (2.8) | ||
| Education | 7.4 (1.8) | 7.2 (1.8) | |
| Family income | 4.3 (1.8) | 4.1 (1.7) | |
| Alcohol (drinks/week) | 2.4 (4.9) | 2.7 (5.3) | 5.4 (6.5) |
| PA (MET h/week) | 9.3 (2.5, 18.8) | 8.3 (2.3, 17.5) | |
| Dietary vitamin D (mcg) | 3.8 (2.4, 5.7) | 3.8 (2.4, 5.7) | |
| Vitamin D (nmol/L) | 50.6 (20.6) | ||
| Number of pregnancies/parity | 2.6 (1.7) | 2.7 (1.7) | 1.9 (1.1) |
| WHO fracture risk score | 9.3 (6.5, 14.3) | 10.6 (7.5, 15.7) | |
| Binary variables | n (%) | ||
| HT trial participant | 8655 (8.1) | 4534 (23.2) | |
| Ca+ & vitamin D trial participant | 11 754 (11.0) | 3733 (19.1) | |
| Hormone use ever | 61 868 (57.9) | 9674 (49.5) | |
| Takes MHT | 4409 (4.6) | ||
| Current smoking | 6945 (6.5) | 1446 (7.4) | 7480 (7.8) |
| Bilateral oophorectomy/oophorectomy history | 6091 (5.7) | 919 (4.7) | 1723 (1.8) |
| Hysterectomy | 31 094 (29.1) | 5257 (26.9) | 2886 (3.0) |
| Hypertension | 23 615 (22.1) | 4788 (24.5) | 45 596 (47.8) |
| Diabetes/T2DM | 3312 (3.1) | 762 (3.9) | 3172 (3.3) |
| Broken bone | 42 955 (40.2) | 8091 (41.4) | |
| Osteoporosis | 8441 (7.9) | 1524 (7.8) | |
| Stroke or transient ischaemic attack | 2885 (2.7) | 625 (3.2) | 1350 (1.4) |
ANM, age of natural menopause; BMI, body mass index; BP, blood pressure; PA, physical activity; Ca+, calcium; WHO, World Health Organization; HT, hormone therapy; MHT, menopausal hormone therapy; T2DM, type 2 diabetes.