CATEGORY: BRAIN & MENTAL HEALTH
Drinking a moderate amount of coffee — around two to three cups of caffeinated coffee a day — was linked to a lower risk of dementia in a large, decades-long study, with the benefit strongest at that moderate level and no extra protection from drinking more. Adults with the highest caffeinated-coffee intake had about an 18% lower risk of dementia than those who drank little or none. Because the study followed people’s own habits rather than assigning them coffee, it shows an association, not proof that coffee protects the brain.1
How the Study Worked
Researchers drew on 131,821 U.S. health professionals in two long-running studies who reported their diets, including coffee and tea, through repeated questionnaires. Participants were followed for up to 43 years, and the team recorded who was diagnosed with dementia — 11,033 people over the course of the study — while also testing memory and thinking. That long follow-up is central to the finding, because dementia develops gradually over decades.
Where the Benefit Peaked
The lowest dementia risk clustered around two to three cups of caffeinated coffee a day (or one to two cups of tea). Drinking more than that didn’t add further protection — but, unlike in some earlier research, it also wasn’t tied to harm. Coffee drinkers were also somewhat less likely to report their own memory slipping: about 7.8% reported such concerns, compared with 9.5% among those who drank little or no caffeinated coffee.1
Why Caffeine May Be the Key
The link appeared only with caffeinated coffee. Decaffeinated coffee showed no benefit, which points to caffeine — rather than coffee’s other compounds — as the likely active ingredient. Caffeine is a stimulant that affects brain signaling, though exactly how it might influence dementia risk over decades isn’t settled.
What This Does and Doesn’t Mean
Because people chose how much coffee to drink, the study can’t prove coffee keeps dementia away, and coffee drinkers may differ from others in ways that affect brain health. It also relied on people accurately recalling their intake over many years. Still, it adds unusually long-term evidence that a moderate coffee habit is linked to better brain health later in life — and that, for the brain, more is not necessarily better.
Key Takeaways
- In a study of more than 131,000 adults followed for up to 43 years, the lowest dementia risk clustered around two to three cups of caffeinated coffee a day, with no added benefit from drinking more.
- Those with the highest caffeinated-coffee intake had about 18% lower dementia risk than those who drank little or none; decaffeinated coffee showed no such link.
- This was an observational study, so it shows an association, not proof that coffee prevents dementia.
- If you have questions about caffeine and your brain health — especially if you limit caffeine for heart, sleep, or other reasons — your healthcare provider can help you weigh what’s right for you.
References
- Zhang Y, Liu Y, Li Y, et al. Coffee and tea intake, dementia risk, and cognitive function. JAMA. 2026;335(11):961–974. link