More Cups of Java May Cut Endometrial Cancer Risk By Charles Bankhead, Staff Writer, MedPage Today
Explain that women who drank at least four cups of coffee daily had a 25% lower risk of endometrial cancer as compared with women who consumed less.
Note that tea consumption was not associated with the risk of endometrial cancer in this study.
Women who drank at least four cups of coffee daily had a 25% lower risk of endometrial cancer as compared with women who consumed less, data from a large prospective cohort study showed.
The reduction in relative risk increased to 30% when compared with women who whose self-reported coffee consumption was less than one cup daily.
The apparent benefit was limited to regular coffee, as consumption of decaffeinated coffee was associated with only a trend toward an inverse relationship with endometrial cancer risk, as reported online in Cancer Epidemiology, Biomarkers & Prevention.
The authors urged caution in extrapolating the results to the general population.
"Our findings provide prospective evidence with the potential beneficial role of four or more cups of coffee per day against endometrial cancer risk," Youjin Je, MS, of Harvard School of Public Health in Boston, and co-authors wrote.
"However, recommendations about high coffee consumption should be made with caution. Because our population is relatively health conscious and thus may tend not to add substantial sugar and cream, the results of risk reduction with four cups of coffee per day may not be generalizable to coffee drinkers who typically add sugar or cream to coffee."
In theory, coffee consumption might influence endometrial cancer risk via caffeine's effects on the female hormonal milieu. Studies have shown that coffee or caffeine intake influenced levels of sex hormone binding globulin, free estradiol, C-peptide, and adiponectin, the authors wrote in their introduction.
Epidemiologic studies have demonstrated an inverse association between coffee consumption and endometrial cancer risk, but most of the data was collected retrospectively. Moreover, few studies attempted to control for caffeine intake or coffee components that might influence endometrial cancer risk.
The prospective Nurses' Health Study (NHS) provided a dataset with characteristics that could address limitations of previous investigations of coffee consumption and endometrial cancer, the authors continued. Initiated in 1976, the NHS accumulated data on 121,700 female nurses who were ages 30 to 55 at enrollment.
Je and colleagues analyzed data on a subgroup of 67,470 NHS participants who completed an initial food frequency questionnaire in 1980 and six follow-up questionnaires until 2002.
Participants were grouped into six categories of coffee consumption, ranging from never/less than once a month to six or more times daily. Investigators converted frequency of coffee consumption into cups per day.
Estimated caffeine consumption was derived from U.S. Department of Agriculture food composition sources, including coffee, tea, cola or other caffeine-containing carbonated drinks, and chocolate.
Investigators also estimated the NHS participants' consumption of alcohol and other potential confounders, and they included data on hormone therapy, smoking history, and other factors that might influence the risk of endometrial cancer.
During 26 years of follow-up, 672 cases of endometrial cancer were documented from patient reports and medical records.
Examination of baseline characteristics by coffee consumption showed that women who consumed the most coffee were more likely to be current or ex-smokers and to have a lower BMI. Daily coffee drinkers consumed more alcohol and less tea as compared with women who drank coffee less frequently.
The age-adjusted relative risk of endometrial cancer declined with increasing coffee consumption, from 1.00 among women who consumed less than one cup daily to 0.61 among women who reported drinking at least four cups daily (P<0.001 for trend).
In a multivariate analysis, the inverse association no longer remained significant except for the comparison of four or more cups of coffee daily versus less than one cup daily (RR 0.75, P=0.02).
Analysis of the type of coffee consumed showed that women who drank four or more cups of caffeinated coffee daily had a relative risk of 0.70 compared with women who drank less than one cup daily (P=0.02). Increasing consumption of decaffeinated coffee was associated with a nonsignificant 22% reduction in the relative risk of endometrial cancer.
Tea consumption had no association with the risk of endometrial cancer.
Subgroup analysis revealed stronger associations between coffee consumption and endometrial cancer in:
Obese women (RR 0.62, P=0.02 for trend)
Current/former smokers (RR 0.65, P=0.02 for trend)
Postmenopausal women (RR 0.74, P=0.04 for trend)
Women not currently using postmenopausal hormone therapy (RR 0.69, P=0.03 for trend)
"To our knowledge this is the largest prospective cohort study that has evaluated coffee and tea consumption using repeated dietary questionnaires, and the first study to examine the long-term intake of decaffeinated coffee on risk of endometrial cancer," the authors wrote in their discussion of the findings.
"We carefully controlled for potential confounders in the analysis, but we cannot rule out the possibility of residual confounding," they added.
"Unmeasured factors associated with coffee drinking habit may also have influenced our results. However, the factors are more likely to be related to unhealthy lifestyles rather than healthy lifestyles, which make the observed association more inverse after adjusting for the factors."
The study was supported by the National Institutes of Health.
Primary source: Cancer Epidemiology, Biomarkers & Prevention
Je Y, et al "A prospective cohort study of coffee consumption and risk of endometrial cancer over a 26-year follow-up" Cancer Epidemiol Biomarkers Prev 2011; DOI: 10.1158/1055-9965.EPI-11-0766.