Coffee Linked to 18% Lower Dementia Risk in Study

A study published February 10, 2026, in the Journal of the American Medical Association found that daily consumption of two to three cups of caffeinated coffee was associated with an 18% lower risk of developing dementia compared to those who drank the least, according to NBC News. Drinking one to two cups of caffeinated tea per day was associated with a 14% lower risk relative to the lowest consumers. The research analyzed data from 131,821 health professionals tracked across two major longitudinal studies spanning 1986 to 2023, making it one of the largest and longest-running analyses of caffeine and cognitive health on record.

The study was conducted by scientists at Mass General Brigham, the Harvard T.H. Chan School of Public Health, and the Broad Institute of MIT and Harvard. Lead author Dr. Yu Zhang, a research trainee at Mass General Brigham, told NBC News the findings were intended to be reassuring for current coffee drinkers - not a recommendation for non-drinkers to start.

How the Study Was Conducted

The research drew from two existing health datasets. The first - the Nurses’ Health Study - tracked more than 86,000 women with an average age of 46. The second - the Health Professionals Follow-Up Study - included more than 45,000 men averaging age 54. Participants completed diet questionnaires every two to four years and reported their intake of caffeinated coffee, decaffeinated coffee, and tea, according to NBC News.

After a median follow-up period of nearly 37 years, more than 11,000 participants had received a dementia diagnosis. Researchers then cross-referenced beverage consumption patterns against cognitive health outcomes over time. The 18% reduced risk tied to caffeinated coffee applied most strongly among adults aged 75 and younger. The protective association was also observed in participants who carried the APOE4 gene - a significant genetic risk factor for Alzheimer’s disease.

What Made the Difference: Caffeine, Not Decaf

Decaffeinated coffee did not produce the same results. Researchers found no equivalent protective association for decaf drinkers, according to NBC News. That finding points caffeine itself as a key variable - though experts cautioned that isolating caffeine’s effect from coffee’s many other bioactive compounds remains methodologically difficult.

Dr. Kellyann Niotis, a preventive neurologist at Weill Cornell Medicine who was not involved in the study, told NBC News that coffee and tea both contain polyphenols - compounds with antioxidant and anti-inflammatory properties - that may interact with caffeine to produce the observed effect. The standard decaffeination process, she noted, removes not just caffeine but also some of these polyphenols, complicating direct comparisons.

Limitations Researchers Identified

The study is observational, meaning it identifies associations rather than proving cause and effect. CBS News reported that Dr. Celine Gounder, a CBS News medical contributor, recommended interpreting the results with significant caution given that design. Participants self-reported their caffeine intake, which introduces potential measurement error. The study also did not account for coffee preparation method, roast level, or what participants added to their drinks - factors that could influence the concentration of relevant compounds.

Researchers also noted that the dementia diagnosis data came from health records rather than neurological evaluations, which may affect precision. The finding that total caffeine intake - not just coffee - correlated with lower dementia risk adds some support to the caffeine hypothesis, but the authors acknowledged that dementia cannot be prevented through dietary changes alone.

What the Numbers Represent

Globally, 57 million people were living with dementia in 2021, according to the World Health Organization, with Alzheimer’s disease as its most common form and women disproportionately affected, per NBC News. In the United States, the Alzheimer’s Association estimates more than 7 million Americans are currently living with Alzheimer’s. Against that backdrop, an 18% reduction in risk at the population level - if the association reflects a genuine effect - would translate to a meaningful number of cases. The study’s authors and independent experts agreed that further research is needed to understand the mechanisms before any clinical guidance changes.

References: Drinking 2 to 3 cups of coffee or tea daily may help reduce dementia risk, new research finds | What to know about a new study on coffee, tea, caffeine and dementia risk