Reproductive, menstrual, and medical risk factors for endometrial cancer: Results from a case-control study

OBJECTIVE: Our objective was to evaluate the risk for endometrial cancer in relation to reproductive, menstrual, and medical factors. STUDY DESIGN: A case-control study of 405 endometrial cancer cases and 297 population controls in five areas of the United States enabled risk to be evaluated. RESULTS: A major risk factor was the absence of a prior pregnancy (relative risk 2.8, 95% confidence interval 1.7 to 4.6). The protective effect of pregnancy appeared to reflect the influence of term births, because spontaneous and induced abortions were unrelated to risk. Among nulliparous women infertility was a significant risk factor, with women having sought medical advice having nearly eight times the risk of those without difficulty conceiving. After adjustment for other reproductive characteristics, age at first birth and duration of breast-feeding were not related to risk. CONCLUSIONS: Elevated risks were found for subjects reporting early ages at menarche (relative risk 2.4 for ages < 12 vs ≥ 15) and longer days of flow (relative risk 1.9 for ≥ 7 vs < 4 days), but there was no relationship with late ages at natural menopause. Height was not associated with risk, but there was a significant relation to weight, with the risk for 200 versus < 125 pounds being 7.2 (95% confidence interval 3.9 to 13.3). After adjustment for weight and other factors, histories of hypertension and gallbladder disease were not significantly related to risk, but an effect of diabetes persisted (relative risk 2.0, 95% confidence interval 1.1 to 3.6). Hirsutism developing at older ages was also significantly related (relative risk 2.0, 95% confidence interval 1.2 to 3.4).