Menstrual factors and the risk of epithelial ovarian cancer.

The relationship between menstrual factors and the risk of ovarian cancer was evaluated in the framework of a hospital-based case-control study conducted in the greater Milan area on a total of 634 cases of ovarian cancer and 1626 control subjects with a spectrum of acute conditions unrelated to any of the established or potential risk factors for ovarian cancer. Compared with women whose menarche occurred at age 13 or later, the risk of ovarian cancer was moderately (and not significantly) elevated for earlier menarche (multivariate relative risk, RR = 1.13, 95% confidence interval, CI = 0.97-1.37). There was a positive association with age at menopause, the multivariate relative risk, compared with women aged 45 years or less at menopause, being 1.25 for those aged 45-49 years, 1.40 for 50-53 and 1.58 for 54 or over (chi 2(1) trend = 8.86, p = 0.003). A lifelong irregular menstrual pattern (defined as frequent menstrual-like episodes of bleeding less than 21 or more than 35 days apart) was negatively associated with the risk of ovarian cancer (multivariate RR = 0.45, 95% CI = 0.31-0.65). The effect of age at menopause and lifelong menstrual pattern was similar in different strata of age, whereas there was a positive association with early menarche among younger women which disappeared with advancing age. The present findings confirm the influence of various menstrual factors on the risk of epithelial ovarian cancer.(ABSTRACT TRUNCATED AT 250 WORDS)