Table 1.
Characteristics of the participants with data on mammographic density (n = 1,161)
| Mean (SD), median or percentage (n) | |
|---|---|
| Percent mammographic density | 25 (18.1), 21.9 |
| BMI at age 53 (kg/m2) (n = 1,124)a | 27.6 (5.48), 26.5 |
| Age at mammography in years (n = 1,130)a | 51.5 (1.1), 51.5 |
| Age at menarche | |
| <12 | 13% (151) |
| 12 | 22% (255) |
| 13 | 28% (325) |
| 14+ | 16% (186) |
| Missing | 22% (244) |
| Menopausal status at the time of mammography | |
| Pre-menopause | 17% (197) |
| Peri-menopause | 17% (197) |
| Post-menopause | 24% (279) |
| Hysterectomy | 19% (221) |
| HRT/oral contraceptive pill | 18% (209) |
| Unknown | 5% (58) |
| History of hormone therapy use | |
| Never | 54% (627) |
| Ever | 46% (534) |
| Parity | |
| 0 | 12% (139) |
| 1 | 11% (128) |
| 2 | 45% (512) |
| 3 | 22% (255) |
| 4+ | 8% (93) |
| Missing | 2% (23) |
| Smoking status at age 53 | |
| Current smoker | 21% (244) |
| Non-smoker | 77% (894) |
| Missing | 2% (23) |
| Level of physical activity at age 53 | |
| Nil | 48% (557) |
| Moderate | 16% (186) |
| High | 34% (395) |
| Missing | 2% (23) |
an varies due to missing data