November 22, 2011 — Drinking at least 4 cups of coffee per day is associated with a lower risk for endometrial cancer, according to new data from the Nurses' Health Study.
Youjin Je, a doctoral candidate in the lab of Edward Giovannucci, MD, ScD, from the Department of Nutrition and Epidemiology at the Harvard School of Public Health in Boston, Massachusetts, and colleagues published their findings online November 22 in Cancer Epidemiology, Biomarkers & Prevention.
"Coffee consumption may be related to endometrial cancer development due to the potential role of caffeine," Dr. Giovannucci and colleagues write. "Several epidemiologic studies have reported an inverse association between coffee intake and endometrial cancer risk, but data from prospective studies are limited."
Therefore, the researchers prospectively examined the link between drinking coffee and endometrial cancer risk, using prospective data from the Nurses' Health Study.
The analysis included data from 67,470 women aged 34 to 59 years in 1980. Cumulative average coffee intake was determined by questionnaire. During 26 years of follow-up, researchers documented 672 cases of endometrial cancer.
Drinking fewer than 4 cups of coffee per day was not associated with a change in endometrial cancer risk compared with drinking 1 or less cups per day. The researchers accounted for numerous factors in their multivariable analysis, including BMI, age at menopause, age at menarche, parity and age at last birth, oral contraceptive use, postmenopausal hormone use, and smoking and alcohol consumption.
However, drinking 4 or more cups of coffee per day was associated with a 25% relative risk reduction compared with consuming less than 1 cup daily (multivariable rate ratio, 0.75; 95% confidence interval [CI], 0.57 - 0.97; P trend = .02). Drinking between 2 and 3 cups of coffee per day was linked with a 7% reduced risk, but the difference did not reach statistical significance (rate ratio, 0.93; 95% CI, 0.76 - 1.14; P trend = .02).
In terms of absolute risk reduction, women who drank 4 or more cups of coffee reduced their risk for endometrial cancer from 56 cases per 100,000 women to 35 cases per 100,000 women. The investigators saw a similar association when they restricted their analysis to caffeinated coffee consumption. In that case, there was a 30% relative risk reduction in endometrial cancer risk associated with consumption of 4 or more cups compared with less than 1 cup a day.
For decaffeinated coffee consumption, drinking 2 or more cups per day was linked with a 22% relative reduction in risk for endometrial cancer vs drinking less than 1 cup per month, but the difference did not reach statistical significance, perhaps because of the smaller cohort size (relative risk, 0.78; 95% CI, 0.57 - 1.08; P trend = .58). The researchers saw no association between tea drinking and endometrial cancer risk.
In subgroup analyses, there was a stronger inverse association with high coffee intake among obese women. "Because obese women tend to have insulin resistance, oxidative stress, and relatively low levels of [sex hormone binding globulin], the potential abilities of coffee to improve those conditions may have contributed to a decreased risk of endometrial cancer among obese women," the authors write.
"Coffee has already been shown to be protective against diabetes due to its effect on insulin," noted Dr. Giovannucci in a written release. "So we hypothesized that we'd see a reduction in some cancers as well." According to Dr. Giovannucci, laboratory testing has found that coffee has many more antioxidants than most vegetables and fruits.
The authors have disclosed no relevant financial relationships.
Cancer Epidemiol Biomarkers Prev. Published online November 22, 2011.
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Cite this: Coffee Linked to Lower Endometrial Cancer Risk - Medscape - Nov 22, 2011.