Benefits with or without known heart disease
The researchers identified 382,535 participants in the UK Biobank cohort who were free of CVD at baseline. Their median age was 57, and 52% were women.
Those who reported regular daily intake of two to three cups of coffee, compared with those who were not coffee drinkers, showed significantly reduced risks of CVD (hazard ratio, 0.91; 95% confidence interval, 0.88-0.94), CHD (HR, 0.90; 95% CI, 0.87-0.93), heart failure (HR, 0.85; 95% CI, 0.81-0.90), arrhythmias (HR, 0.92; 95% CI, 0.88-0.95), and death from any cause over 10 years (HR, 0.86; 95% CI, 0.83-0.90) (P < .01 for all endpoints).
The risk of CVD death hit its lowest point at an intake of one cup per day (HR, 0.83; 95% CI, 0.75-0.93). The risk of stroke was lowest at less than one cup per day (HR, 0.85; 95% CI, 0.75-0.96).
A separate analysis found similar outcomes among a different subset of UK Biobank participants with recognized CVD at baseline. Among 34,279 such persons, those who drank two to three cups of coffee per day, compared with non–coffee drinkers, showed a reduced risk of death over 10 years (HR, 0.92; 95% CI, 0.86-0.99; P = .03).
Among the 24,111 persons diagnosed with arrhythmias at baseline, the lowest mortality risk was observed at one cup per day (HR, 0.85; 95% CI, 0.78-0.94; P < .01). Among those with atrial fibrillation or atrial flutter, one cup per day was associated with a mortality HR of 0.82 (95% CI, 0.73-0.93; P < .01).
In still another analysis of UK Biobank cohort, incident CVD and mortality during the 10-year follow-up was similarly reduced among participants who reported consumption of brewed ground coffee and, separately, instant coffee, compared with non–coffee drinkers. Decaffeinated coffee showed a mostly neutral or inconsistent effect on the clinical endpoints.
The lowest CVD risk was observed at two to three cups per day among those regularly drinking ground coffee (HR, 0.83; 95% CI, 0.79-0.87) and those predominantly taking instant coffee (HR, 0.91; 95% CI, 0.88-0.95).
Potential mechanisms, study limitations
“Caffeine blocks adenosine receptors, which may explain its potential mild antiarrhythmic properties,” Dr. Kistler said. “Regular coffee drinkers with supraventricular tachycardia coming to the emergency department often need higher adenosine doses to revert.”
Dr. Peter M. Kistler
Caffeine has a role in weight loss through inhibition of gut fatty acid absorption and increase in basal metabolic rate, Dr. Kistler added, and coffee has been associated with a significantly reduced risk of new-onset type 2 diabetes.
However, coffee beans contain more than 100 biologically active compounds, he noted. They include antioxidant polyphenols that reduce oxidative stress and modulate metabolism. Better survival with habitual coffee consumption may be related to improved endothelial function, circulating antioxidants, improved insulin sensitivity, or reduced inflammation, the researchers noted.
They acknowledged some limitations to the analyses. Cause and effect can’t be determined from the observational data. Also, a cup of coffee in the United Kingdom means about 200-250 mL of brew, but its actual caffeine content can vary from 90 mg to 250 mg. Also, data regarding added sugar or milk was lacking. And UK Biobank participants are predominantly White, so the findings may not be generalizable to other populations.
A version of this article first appeared on Medscape.com.