Scientists tracked coffee drinkers for dementia risk over 43 years. Here’s what they found

There’s long been debate as to whether coffee is good for you. But this new study suggests that caffeinated coffee, as well as caffeinated tea, could lead to lower incidence of dementia. So if your morning routine involves making a bleary-eyed beeline to the coffee maker immediately upon waking—you may be doing something right.

The study comes from researchers at Mass General Brigham and the Broad Institute of Harvard University and MIT, and was recently published in the Journal of the American Medical Association. The teams studied 131,821 individuals from two cohorts: one group of men and one group of women in the U.S., all of whom did not have diseases like dementia, cancer, or Parkinson’s at the start of the study. The researchers followed up with the participants to track their coffee and tea drinking habits every two to four years, with some follow-ups even after 43 years, from the early 1980s to 2023.

What the researchers discovered was that moderate amounts of caffeinated coffee and tea may have protective effects on the brain, particularly when it comes to staving off dementia: Of the participants, 11,033 developed dementia over the course of the study. Those who consumed more caffeinated coffee or caffeinated tea had an 18% lower risk of developing dementia when compared with those who did not.

The same participants who consumed caffeinated coffee or tea performed better on questionnaire-based cognitive assessments, and experienced lower rates of cognitive decline: 7.8% compared to 9.5% of the non-coffee drinkers. The results did not hold true for participants who drank decaffeinated coffee or tea. 

This finding is significant, the teams say, because the link between coffee and health effects—particularly caffeinated versus decaffeinated—has been unclear.

The benefits also held for people genetically predisposed to dementia.

“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, a PhD student at Harvard Chan School and a research trainee at Mass General Brigham, per Science Daily.

So, how much coffee or tea should you drink to support your brain health? According to the research, the biggest protective effects were seen in “moderate” caffeine intake. Those who drank two to three cups of coffee daily, or one to two cups of tea daily, saw the biggest brain benefits.

Per previous research, drinking your caffeinated beverage sans cream and sugar offers benefits to your heart and may lengthen your lifespan, too. 

Dr. Daniel Wang, associate scientist with the Channing Division of Network Medicine in the Mass General Brigham Department of Medicine and assistant professor at Harvard Medical School, says the latest results are certainly “encouraging.” But he noted that the “effect size” is still relatively small, and that “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,” he said.