Kotsopoulos et al. previously reported a significant 15% reduction in BRCA1-associated breast cancer risk for each year of menarcheal delay, and a 54% reduction in risk for women whose age at menarche was ≥15 versus ≤11 years of age (odds ratio (OR) = 0.46; 95% CI 0.30–0.69; p-trend = 0.002) [25]. Here, BRCA1 is linked to breast cancer.