Background: Caffeine has been shown to prevent ultraviolet radiation-induced carcinogenesis and to inhibit growth of melanoma cells in experimental studies. We evaluated the association among caffeine intake, coffee consumption, and melanoma risk among three large cohort studies.
Methods: The analysis used data from 89,220 women in the Nurses' Health Study II (1991-2009), 74,666 women in the Nurses' Health Study (1980-2008), and 39,424 men in the Health Professionals Follow-up Study (1986-2008). We used Cox proportional hazards models to estimate the hazard ratios (HR) with 95% confidence intervals (CIs) of melanoma associated with dietary intakes.
Results: We documented 2,254 melanoma cases over 4 million person-years of follow-up. After adjustment for other risk factors, higher total caffeine intake was associated with a lower risk of melanoma (≥393 mg/day vs. <60 mg/day: HR = 0.78, 95% CI = 0.64, 0.96; Ptrend = 0.048). The association was more apparent in women (≥393 mg/day vs. <60 mg/day: HR = 0.70, 95% CI = 0.58, 0.85; Ptrend = 0.001) than in men (HR = 0.94, 95% CI = 0.75, 1.2; Ptrend = 0.81), and more apparent for melanomas occurring on body sites with higher continuous sun exposure (head, neck, and extremities; ≥393 mg/day vs. <60 mg/day: HR = 0.71, 95% CI = 0.59, 0.86; Ptrend = 0.001) than for melanomas occurring on body sites with lower continuous sun exposure (trunk including shoulder, back, hip, abdomen, and chest; HR = 0.90, 95% CI = 0.70, 1.2; Ptrend = 0.60). This pattern of association was similar to that for caffeinated coffee consumption, whereas no association was found for decaffeinated coffee consumption and melanoma risk.
Conclusions: Increasing caffeine intake and caffeinated coffee consumption is associated with decreased risk of cutaneous malignant melanomas.