The menopause and breast cancer.

Abstract

It is usually accepted that an older age of menopause is associated with an increased risk of breast cancer. This is often interpreted as a statement about postmenopausal women; however, some authors, eg ref. 1, explicitly and others, eg ref. 2, implicitly take it as embracing both an increased risk for postmenopausal women who have had a late menopause and an increased risk for older premenopausal women who are still menstruating. We have recently examined the role of menstrual status and age at menopause in a study of risk factors in a population of screened women.3 Our results there and the difficulties we encountered in relating them to the literature have motivated this study. We begin with a survey of the literature: comparison of reported studies is difficult because of considerable variations in the definitions of menstrual status (as well as absence and vagueness of definitions), the frequent absence of any menopausal category, and a lack of age-specific figures. The only clear consensus is that there is a higher risk among women aged 50-54 who are still menstruating than among those who are postmenopausal. Later we propose a modification of the two linear component model for age incidence: this includes increased incidence at the time of the menopause and a subsequent deficit. The intention is to test this model using data from the Edinburgh Breast Screening Trial, and the suitability for this purpose of the data which are being collected is discussed.