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Table 5 Age at menarche and breast cancer risk by ER/PR status

From: Reproductive factors and breast cancer risk according to joint estrogen and progesterone receptor status: a meta-analysis of epidemiological studies

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
  1. Test for homogeneity across all studies: P ER+PR+ = 0.95 and P ER-PR- = 0.23. Egger's test for publication bias for all studies: P ER+PR+ = 0.42 and P ER-PR- = 0.55. CI, confidence interval; ER+, estrogen receptor-positive; ER-, estrogen receptor-negative; ER/PR, estrogen and progesterone receptor; MP, menopausal or menopause; Per 2 years↑, Per 2 years' increase in age at menarche; PR+, progesterone receptor-positive; PR-, progesterone receptor-negative; RR, relative risk.