Moderate coffee consumption has been inversely associated with mortality; however, does heavy intake, particularly among those with common genetic polymorphisms that impair caffeine metabolism, increase risk of mortality?
This large prospective cohort study of a half million people found inverse associations for coffee drinking with mortality, including among participants drinking 1 up to 8 or more cups per day. No differences were observed in analyses that were stratified by genetic polymorphisms affecting caffeine metabolism.
This study provides further evidence that coffee drinking can be part of a healthy diet and offers reassurance to coffee drinkers.
Prospective cohorts in North America, Europe, and Asia show consistent inverse associations between coffee drinking and mortality, including deaths from cardiovascular disease and some cancers. However, concerns about coffee, particularly among people with common genetic polymorphisms affecting caffeine metabolism and among those drinking more than 5 cups per day, remain.
To evaluate associations of coffee drinking with mortality by genetic caffeine metabolism score.
Design, Setting, and Participants
The UK Biobank is a population-based study that invited approximately 9.2 million individuals from across the United Kingdom to participate. We used baseline demographic, lifestyle, and genetic data form the UK Biobank cohort, with follow-up beginning in 2006 and ending in 2016, to estimate hazard ratios (HRs) for coffee intake and mortality, using multivariable-adjusted Cox proportional hazards models. We investigated potential effect modification by caffeine metabolism, defined by a genetic score of previously identified polymorphisms in AHR, CYP1A2, CYP2A6, and POR that have an effect on caffeine metabolism. Of the 502 641 participants who consented with baseline data, we included those who were not pregnant and had complete data on coffee intake and smoking status (n = 498 134).
Total, ground, instant, and decaffeinated coffee intake.
Main Outcomes and Measures
All-cause and cause-specific mortality.
The mean age of the participants was 57 years (range, 38-73 years); 271 019 (54%) were female, and 387 494 (78%) were coffee drinkers. Over 10 years of follow-up, 14 225 deaths occurred. Coffee drinking was inversely associated with all-cause mortality. Using non–coffee drinkers as the reference group, HRs for drinking less than 1, 1, 2 to 3, 4 to 5, 6 to 7, and 8 or more cups per day were 0.94 (95% CI, 0.88-1.01), 0.92 (95% CI, 0.87-0.97), 0.88 (95% CI, 0.84-0.93), 0.88 (95% CI, 0.83-0.93), 0.84 (95% CI, 0.77-0.92), and 0.86 (95% CI, 0.77-0.95), respectively. Similar associations were observed for instant, ground, and decaffeinated coffee, across common causes of death, and regardless of genetic caffeine metabolism score. For example, the HRs for 6 or more cups per day ranged from 0.70 (95% CI, 0.53-0.94) to 0.92 (95% CI, 0.78-1.10), with no evidence of effect modification across strata of caffeine metabolism score (P = .17 for heterogeneity).
Conclusions and Relevance
Coffee drinking was inversely associated with mortality, including among those drinking 8 or more cups per day and those with genetic polymorphisms indicating slower or faster caffeine metabolism. These findings suggest the importance of noncaffeine constituents in the coffee-mortality association and provide further reassurance that coffee drinking can be a part of a healthy diet.
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I wondered how this study could be conclusive if it didn't mention details on anything added to coffee (i.e., sugar, cream, dairy milk, almond milk, etc.) and the amount of said additions, as well as how many times (every cup or just sometimes) those were added. Also, how many people had straight, black coffee?
Seems many relevant factors were overlooked or left out.
Loftfield E, Cornelis MC, Caporaso N, Yu K, Sinha R, Freedman N. Association of Coffee Drinking With Mortality by Genetic Variation in Caffeine MetabolismFindings From the UK Biobank. JAMA Intern Med. 2018;178(8):1086–1097. doi:10.1001/jamainternmed.2018.2425
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