Long-term alcohol intake and risk of endometrial cancer in the Nurses' Health Study, 1980–2010

BACKGROUND: Previous epidemiologic studies have shown inconsistent results for the association between alcohol intake and endometrial cancer risk. Most of the studies, however, assessed alcohol intake after cancer diagnosis, or measured alcohol intake at baseline only. METHODS: We prospectively examined the association between alcohol intake and endometrial cancer risk in the Nurses' Health Study with 68 067 female participants aged 34–59 years in 1980. Alcohol intake was measured several times with validated dietary questionnaires. We calculated cumulative average alcohol intake to represent long-term intakes of individual subjects. Using Cox proportional hazards models, we estimated incidence rate ratios (RRs) and 95% confidence intervals (CIs) for endometrial cancer risk after controlling for several risk factors simultaneously. RESULTS: We identified a total of 794 invasive endometrial adenocarcinoma from 1980 to 2010. We found an inverse association among alcohol drinkers (multivariable RR=0.81; 95% CI: 0.68–0.96) compared with nondrinkers. Women with light alcohol intake of <5 g per day (∼half drink per day) had a 22% lower risk of endometrial cancer (multivariable RR=0.78; 95% CI: 0.66–0.94). Higher intake of alcohol, however, did not provide additional benefits against endometrial cancer: multivariable RRs for 5–14.9 g (∼1 drink), 15–29.9 g (∼2 drinks), or ⩾30 g (⩾2 drinks) versus 0 g per day were 0.88, 0.83, and 0.78 (95% CI: 0.49–1.25), respectively. The lower risk among drinkers (∼half drink per day) appeared to be stronger for obese women, but no significant interaction by body mass index was found. CONCLUSIONS: This study provides prospective evidence for an inverse association between light alcohol intake (∼half drink per day) in the long term and endometrial cancer risk, but above that level no significant association was found.