You probably have a routine for your morning coffee. Maybe one cup to wake up, maybe another with breakfast. Most of us never stop to wonder whether that habit is doing anything for the brain years down the line.
Harvard researchers have now looked at it, and the answer is more specific than most would guess.
Adults who drank two to three cups of caffeinated coffee a day had an 18 percent lower risk of dementia compared with those who barely drank any.
The analysis followed 131,821 US nurses and health professionals for up to 43 years, with a median follow-up of nearly 37 years. It was published in JAMA on February 9, 2026.
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Over that stretch, 11,033 participants developed dementia. The strongest protective link appeared at the two to three cup mark.
Why decaf did not share the benefit
Decaffeinated coffee showed no clear link to lower dementia risk or better cognitive performance in the analysis. That points to caffeine itself as the likely driver.
Tea followed a similar pattern. One to two cups a day was tied to about a 14 percent lower dementia risk.
The study could not separate caffeinated from decaffeinated tea, so that signal is harder to read.
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Self-reported memory and thinking problems were also less common among coffee drinkers.
About 7.8 percent of higher caffeine consumers reported subjective cognitive decline, versus 9.5 percent of those who rarely drank coffee.
What the numbers mean in practice
Senior author Daniel Wang, from Harvard Medical School and Mass General Brigham, told the Harvard Gazette that the benefit is real but modest.
"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," he said.
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The protective link did not grow stronger for people who drank four or more cups a day. More coffee was not more protection.
The pattern also held across people with both low and high genetic risk for dementia.
The study is observational, so it cannot prove that coffee itself protects the brain.
The researchers note the signal held across age, sex, and genetic background, and they point to caffeine as the most likely driver behind the effect seen in regular coffee drinkers.
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This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.