This was a large prospective cohort study of a half million people (whose records were selected from the UK Biobank) revealing the inverse associations for coffee drinking with mortality, including 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.
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, remained and have now been further elucidated. Among other parameters, the study investigated potential effect modification by caffeine metabolism, defined by a genetic score of previously identified polymorphisms in the AHR, CYP1A2, CYP2A6, and POR genes that have an effect on caffeine metabolism. Of the 502’ 641 participants who consented with baseline data those who were not pregnant and had complete data on coffee intake and smoking status (n = 498’ 134) were included.
Overall, in the study, scientifically seen, the data are very impressive and show that 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).