Table 5 Age at menarche and breast cancer risk by ER/PR status
Study | Subgroups by MP status | Exposure categories (n) | Oldest/Youngest age category | RR (95% CI) for oldest vs. youngest age category | |
|---|---|---|---|---|---|
ER+PR+ | ER-PR- | ||||
Cohort studies | |||||
[9] | Post-MP | 2 | ≥13/<13 | 0.69 (0.56–0.85) | 1.07 (0.67–1.71) |
[10] | All women | 2 | 15/11 | 0.68 (0.62–0.73) | 0.78 (0.68–0.89) |
Summary RRs for cohort studies | 0.68 (0.59–0.79) | 0.80 (0.69–0.93) | |||
Population-based case-control studies | |||||
[11] | All women | 2 | ≥12/<12 | 0.67 (0.50–0.91) | 0.91 (0.67–1.43) |
Pre-MP | 2 | ≥12/<12 | 0.67 (0.4–1.0) | 1.11 (0.67–1.67) | |
Post-MP | 2 | ≥12/<12 | 0.63 (0.42–1.0) | 0.77 (0.45–1.43) | |
[12] | Young | 2 | ≥13/<13 | 0.77 (0.63–0.94) | 0.78 (0.61–1.00) |
[13] | All women | 4 | ≥14/<12 | 0.72 (0.52–0.99) | 0.99 (0.63–1.53) |
Pre-MP | 4 | ≥14/<12 | 0.49 (0.31–0.76) | 1.12 (0.62–2.03) | |
Post-MP | 4 | ≥14/<12 | 0.84 (0.64–1.10) | 0.94 (0.64–1.37) | |
[14] | Young | ≥13/<13 | 0.8 (0.6–1.1) | 0.6 (0.4–0.9) | |
[8] | Young | 4 | ≥14/<12 | 0.60 (0.42–0.86) | 0.59 (0.38–0.92) |
Summary RRs for population-based case-control studies | 0.73 (0.59–0.89) | 0.77 (0.63–0.94) | |||
Hospital-based case-control studies | |||||
[15] | All women | Per 2 years↑ | 2 years' increase | 0.83 (0.68–1.01) | 1.11 (0.91–1.36) |
16 | All women | 3 | ≥14/<12 | 1.0 (0.53–-2.00) | 1.43 (0.71–2.50) |
Summary RRs for hospital-based case-control studies | 0.84 (0.64–1.10) | 1.14 (0.87–1.49) | |||
Summary RRs by MP status | Pre-MP/Young | 0.71 (0.57–0.88) | 0.77 (0.62–0.95) | ||
Post-MP | 0.74 (0.54–1.01) | 0.95 (0.70–1.30) | |||
Summary RRs for all studies | 0.72 (0.64–0.80) | 0.84 (0.75–0.94) | |||
P for homogeneity between ER+PR+ and ER-PR- cancer | p = 0.006 | ||||