MENSTRUAL AND REPRODUCTIVE CHARACTERISTICS AND AGE AT NATURAL MENOPAUSE

Data from women who enrolled between 1935 and 1939 in a long-term prospective study of menstrual and reproductive health, in which menstrual cycles other events were recorded as they occurred, were analyzed to examine factors associated with age at natural menopause. Analysis was restrictedwomen who enrolled before age 25 years and recorded data through at least 44 years. Women with a median cycle length that was less than 26 days ages 20-35 years reached menopause 1.4 years earlierthan those with cycles between 26 and 32 days. The difference in mean menopausal age between womenwith short cycle length (less than 26 days) and women with long cycle length (33 days orlonger) was 2.2 years. Women who had ever been pregnant reached menopause slightly, but statistically significantly, later than women never been pregnant Similarly, women who had ever had a livebirth had slightly later age at menopause compared with nulliparous women. A trend later age at menopause withincreasing parity was also observed. There was association with age at menarche. Certain of these observations are consistent proposed mechanisms of cessation of menstrual function. © 1990 by The Johns Hopkins University School of Hygiene and Public Health.