A large prospective cohort study found that drinking 2-3 cups of coffee or 1-2 cups of tea daily was linked to an 18% lower dementia risk and improved cognitive performance over a follow-up period of 43 years compared to non-drinkers, including participants at heightened dementia risk. The study, published in JAMA, was conducted by researchers from Mass General Brigham, Harvard T.H. Chan School of Public Health, and the Broad Institute of MIT and Harvard.

“When searching for possible dementia prevention tools, we thought something as prevalent as coffee may be a promising dietary intervention, and our unique access to high quality data through studies that has been going on for more than 40 years allowed us to follow through on that idea,” said senior author Daniel Wang, MD, ScD, associate scientist at Mass General Brigham and assistant professor at Harvard Medical School. “While our results are encouraging, it’s important to remember that the effect size is small and there are lots of important ways to protect cognitive function as we age. Our study suggests that caffeinated coffee or tea consumption can be one piece of that puzzle.”

Coffee and tea are each rich in polyphenols and caffeine, which are thought to support brain health. These substances may help reduce inflammation and limit cellular damage, both of which are linked to cognitive decline. Research on the topic to date has provided mixed results, often due to shorter study periods or data limitations.

The present study, however, used datasets where participants were tracked for 43 years, with repeated evaluations of diet, dementia diagnoses, subjective cognitive concerns, and objective cognitive performance.

Among more than 130,000 participants, 11,033 developed dementia over the course of the study. Individuals who consumed higher amounts of caffeinated coffee had an 18% lower risk of developing dementia compared with those who rarely or never drank it. They also reported lower rates of subjective cognitive decline (7.8% versus 9.5%) and performed better on certain cognition tests.

Don’t Count Out Caffeine

Decaffeinated coffee didn’t show the associations seen with caffeinated tea and coffee, suggesting that caffeine may be an important factor behind the observed benefits. The strongest effects were observed in those averaging 2-3 cups of coffee or 1-2 cups of tea per day, but higher levels of caffeine didn’t appear to cause harm and had comparable benefits.

“We also compared people with different genetic predispositions to developing dementia and saw the same results, meaning coffee or caffeine is likely equally beneficial for people with high and low genetic risk of developing dementia,” said lead author Yu Zhang, MBBS, MS, PhD, student at Harvard Chan School and research trainee at Mass General Brigham.