Table 4.

Age at menarche and breast cancer risk stratified by hormone receptor expression

First author (reference)Country (study)Cases (n)Age at menarche (y)
Risk estimate (95% CI)*
Reference groupAge category
ER+ER−
Kreiger (35)Canada (ON)528<1212-140.8 (0.5-1.1)0.9 (0.5-1.6)
15+0.8 (0.5-1.3)0.7 (0.3-1.5)
Zhu (27)United States (TN)281<1313+1.0 (0.6-1.6)1.2 (0.7-2.1)
Cooper (36)Australia380<13130.9 (0.6-1.5)0.9 (0.6-1.7)
14+1.0 (0.6-2.1)0.8 (0.4-1.4)
Hislop (37)Canada (BC)512<13130.9 (0.7-1.1)0.9 (0.7-1.2)
14+1.0 (0.8-1.2)1.1 (0.8-1.4)
McTiernan (39)United States (CASH-WA)240<1313+1.3 (0.8-1.9)1.8 (1.1-3.0)
Yoo (41)Japan455Per 2 y olderContinuous1.0 (0.9-1.2)1.1 (0.9-1.3)
PR+PR−
Kreiger (35)Canada (ON)528<1212-140.7 (0.5-1.1)0.9 (0.6-1.5)
15+0.8 (0.5-1.3)0.7 (0.4-1.4)
Yoo (41)Japan455Per 2 y olderContinuous0.8 (0.7-1.0)1.2 (1.0-1.4)
ER+/PR+ER−/PR−
Cotterchio (24)Canada (ON)3,276<12Premenopause
120.6 (0.4-0.9)1.1 (0.6-1.9)
130.5 (0.3-0.8)1.1 (0.6-1.8)
14+0.5 (0.3-0.8)1.1 (0.6-2.0)
Postmenopause
121.3 (1.0-1.7)1.0 (0.7-1.5)
131.2 (0.9-1.5)1.0 (0.7-1.4)
14+0.8 (0.6-1.1)0.9 (0.6-1.4)
Huang (32)United States (CBCS)783<1212+0.7 (0.5-0.9)0.9 (0.7-1.4)
McCredie (23)Melbourne (Australia)618<1313+0.8 (0.6-1.1)0.9 (0.5-1.8)
Britton (29)United States (WISH)1,212<1313+0.8 (0.6-0.9)0.8 (0.6-1.0)
Potter (17)United States (IWHS)610<1313+0.7 (0.6-0.9)1.1 (0.7-1.7)
Yoo (41)Japan455Per 2 y olderContinuous0.8 (0.7-1.0)1.1 (0.9-1.4)
  • NOTE: Table excludes Morabia et al. (33), who found that an older age at menarche similarly reduced the risk of both ER+ and ER− breast cancers; however, ORs were not presented in the article.

  • * ORs were the reported risk estimates for case-control studies and RRs for cohort designs.

  • Among African American women.