Associations of coffee consumption with cancer mortality are inconsistent for many types of cancer, and confounding by smoking is an important concern.
Cox proportional hazards regression was used to estimate multivariable-adjusted hazard ratios (HR) for coffee consumption associated with death from all cancers combined and from specific cancer types among 922,896 Cancer Prevention Study-II participants aged 28-94 years who completed a four-page questionnaire and were cancer free at baseline in 1982.
During follow-up through 2012, there were 118,738 cancer deaths. There was a non-linear association between coffee consumption and all-cancer death among current smokers and former smokers and no association among never smokers. Among non-smokers, a 2 cup/day increase in coffee consumption was inversely associated with death from colorectal (HR=0.97; 95% confidence interval [CI] 0.95-0.99), liver (HR=0.92; 95% CI 0.88-0.96), and female breast (HR=0.97; 95% CI 0.94-0.99) cancers, and positively associated with esophageal cancer death (HR=1.07; 95% CI 1.02-1.12). For head and neck cancer, a non-linear inverse association was observed starting at 2-3 cups per day (HR=0.72; 95% CI 0.55-0.95), with similar associations observed at higher levels of consumption.
These findings are consistent with many other studies that suggest coffee drinking is associated with a lower risk of colorectal, liver, female breast and head and neck cancer. The association of coffee consumption with higher risk of esophageal cancer among nonsmokers in our study should be confirmed. Impact: These results underscore the importance of assessing associations between coffee consumption and cancer mortality by smoking status.