Does Early Menarche Cause Breast Cancer?

Earlier age at menarche has been consistently associated with increased risk of both premenopausal and postmenopausal breast cancer. Early menarche may be associated with more rapid onset of regular ovulatory menstrual cycles and hence greater lifetime exposure to endogenous hormones.

Does early menarche increase risk for breast cancer?

Breast cancer risk increased by a significantly greater factor for every year younger at menarche than for every year older at menopause, indicating that menarche and menopause may not affect breast cancer risk merely by extending women's total reproductive years.

Does early puberty cause breast cancer?

Earlier and potentially prolonged exposure to high levels during puberty may increase breast cancer risk as well. We found that earlier age at thelarche, which represents the onset of this period of rapid breast development, was associated with an increased risk of breast cancer.