Table 1. Characteristics of participants.
| Invasive breast cancer | Controls | P-value | |
|---|---|---|---|
| Number | 1088 | 4815 | — |
| Age (years) | 62 (29–93) | 61 (22–90) | <0.0001 |
| Body mass index (kg m−2) | 24 (14–51) | 24 (13–50) | 0.0001 |
| Alcohol consumption (g week−1) | 48 (0–720) | 36 (0–960) | 0.0002 |
| Nulliparous (%) | 13 (11–16) | 25 (24–26) | <0.0001 |
| Use of oral contraceptive pill (%) | 3 (1–4) | 4 (4–5) | 0.02 |
| Postmenopausal (%) | 76 (73–79) | 71 (69–72) | 0.0009 |
| Use of hormonal replacement therapy (%) | 31 (27–34) | 16 (15–17) | <0.0001 |
Values represent median (range) or frequencies (95% confidence interval).
P-values are for invasive breast cancer vs controls on Mann–Whitney U-test or Pearson's χ2 test.