Morning Coffee May Slow Dementia Risk, Longest Study Yet Finds
A 43-year study of 131,000 people suggests regular coffee drinkers may have 18% lower dementia risk, though researchers caution the effect is modest and not a magic solution.
For most people, the morning cup is about waking up, not warding off disease. But a new 43-year study tracking more than 131,000 people suggests the caffeine in coffee and tea may offer something more: a measurable reduction in dementia risk.
People who drank the most caffeinated coffee showed an 18 percent lower risk of developing dementia compared to those with the lowest intake. The benefit appeared to plateau at two to three cups daily, researchers reported.
Published in JAMA on Feb. 9, the research followed nurses and health professionals for up to 43 years, identifying 11,033 dementia cases. The study included 86,606 women from the Nurses' Health Study and 45,215 men from the Health Professionals Follow-Up Study.
The authors described it as the best evidence to date on caffeine and cognitive health, owing largely to its massive sample size and decades-long follow-up.
Decaffeinated coffee showed no significant association with dementia risk reduction, suggesting the caffeine itself—not just the act of drinking coffee—is the active ingredient.
"I would say it's the best evidence we have so far on the association of caffeine and cognitive health," said lead author Yu Zhang, a research trainee at Mass General Brigham.
For millions who already start their day with coffee, the findings offer a small but meaningful reassurance. But senior author Daniel Wang, MD, ScD, of Harvard Medical School and Mass General Brigham, tempered enthusiasm with realism. He described the effect size as small and emphasized that caffeine is only one piece of the cognitive health puzzle.
"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," Wang said. "Our study suggests that caffeinated coffee or tea consumption can be one piece of that puzzle."
The study relied on self-reported beverage intake, assessed repeatedly throughout the follow-up period. Researchers controlled for smoking, exercise, diet and other health conditions that could influence dementia risk. Still, independent experts raised questions about whether the observational design could truly isolate caffeine as the cause.
"This is a well-conducted study for the type of data available," said Prof. Naveed Sattar of the University of Glasgow, a cardiometabolic medicine specialist. "However, because it uses observational, not experimental, evidence, the findings can only be considered suggestive."
Sattar noted that coffee and tea drinkers may lead healthier lives overall, and those broader lifestyle patterns—not the beverages themselves—could explain the association.
The study included genetic analysis that showed benefits regardless of APOE4 genetic risk status, a gene variant linked to higher Alzheimer's disease risk.
"We also compared people with different genetic predispositions to developing dementia and saw the same results," Zhang said. "Meaning coffee or caffeine is likely equally beneficial for people with high and low genetic risk of developing dementia."
That finding may offer comfort to those who carry the gene and fear a predetermined fate. But Dr. Susan Kohlhaas, executive director of research at Alzheimer's Research UK, cautioned against overinterpreting the findings.
"This research doesn't prove that coffee or tea protect the brain," she said. "There's no single food or drink that can prevent dementia."
For readers already drinking coffee or tea, the study offers reassurance rather than a call to action. For those who don't, it may reframe a daily habit in a new light, but it is not a reason to start.
"Don't think of coffee or tea as a magic shield," Zhang said. "I'd say maintaining a healthy lifestyle, getting regular exercise, having a balanced diet and getting good sleep are all important to get better brain health."