Moderate caffeine intake was associated with a decreased risk for all-cause mortality, regardless of the presence or absence of coffee consumption, according to findings recently published in Mayo Clinic Proceedings.
“Few studies have investigated the association between daily caffeine intake and mortality, and no study has yet evaluated the effects of caffeine intake compared with no caffeine intake,” Tetsuro Tsujimoto, MD, PhD, National Center for Global Health, Tokyo, and colleagues wrote.
Researchers conducted a prospective cohort study using data from 17,568 participants of the National Health and Nutrition Examination Survey 1999-2010. Cox proportional hazards models were used to compare the multivariate-adjusted HRs of participants with varying caffeine intake over the course of a day. The mean interquartile range of follow-up was 6.5 ± 2.8 years.
Tsujimoto and colleagues found that compared with those who had a caffeine intake of less than 10 mg per day, HRs for all-cause mortality were significantly lower in participants with a caffeine intake of 10 mg to 99 mg per day (HR = 0.81; 95% CI, 0.66-1), 100 mg to 199 mg per day (HR = 0.63; 95% CI, 0.51-0.78), and 200 mg or more per day (HR = 0.69; 95% CI, 0.58-0.83). In addition, a similar association was observed in participants who consumed less than 1 cup of coffee per week, and the HR was lowest in those with a caffeine intake of 100 mg to 199 mg per day (HR = 0.46; 95% CI, 0.22-0.93). An 8-ounce cup of coffee has approximately 95 mg, 8 ounces of tea has approximately 26 mg and a 12-ounce can of cola has about 29 mg.
There was no association between caffeine intake and cardiovascular mortality, whereas the HRs for noncardiovascular mortality were significantly lower in those with a caffeine intake of 10 mg to 99 mg per day (HR = 0.74; 95% CI, 0.57-0.95), 100 mg to 199 mg per day (HR = 0.6; 95% CI, 0.46-0.77), and 200 mg or more per day (HR = 0.65; 95% CI, 0.53-0.8).
“The mechanism of this association is currently unclear and may reflect mere chance or residual confounding. Possible explanations are that caffeine reduces the risk of depression, stimulates the metabolic rate and has beneficial effects on weight control, is a methylxanthine bronchodilator, enhances performance in sustained high-intensity exercise, and is associated with protective effects against some infectious and malignant diseases,” researchers wrote.
“Conversely, the present analyses found no beneficial effects of caffeine intake on cardiovascular mortality, although several studies and a recent meta-analysis found an inverse association between coffee consumption and cardiovascular mortality. Caffeine intake can stimulate sympathetic activity and increase catecholamine levels, leading to significant cardiovascular stress.”
Tsujimoto and colleagues concluded that further studies are needed to determine the effect of caffeine.
Some of the most recent studies adding to the uncertainty include two that appeared this week in Annals of Internal Medicine that suggested coffee, with or without caffeine, was associated with all-cause and cause-specific mortality benefits among people of various ethnicities and cultures. – by Janel Miller
Healio Family Medicine was unable to determine researchers’ relevant financial disclosures prior to publication.