Intake of coffee, caffeine and other methylxanthines and risk of Type I vs Type II endometrial cancer.

BACKGROUND: Coffee and other sources of methylxanthines and risk of Type I vs Type II endometrial cancer (EC) have not been evaluated previously. METHODS: Prospective cohort of 23,356 postmenopausal women with 471 Type I and 71 Type II EC cases. RESULTS: Type I EC was statistically significantly associated with caffeinated (relative risk (RR)=0.65 for 4+ cups per day vs ≤1 cup per month: 95% confidence interval (CI): 0.47-0.89) but not decaffeinated (RR=0.76; 95% CI: 0.50-1.15) coffee intake; there were no associations with tea, cola or chocolate, or for Type II EC. The inverse association with caffeinated coffee intake was specific to women with a body mass index 30+ kg m(-2) (RR=0.56; 95% CI: 0.36-0.89). CONCLUSION: Coffee may protect against Type I EC in obese postmenopausal women.