A large prospective study published in JAMA followed more than 131,000 adults—drawn from the Nurses’ Health Study and the Health Professionals Follow-up Study—for up to 43 years, tracking beverage habits alongside dementia diagnoses and cognitive test scores.

Coffee and Tea May Be the Key to Better Memory

Over that period, more than 11,000 cases of incident dementia were recorded. The distinction between caffeinated and decaffeinated coffee proved to be critical.

Adults who drank the most caffeinated coffee developed dementia at an 18 percent lower rate than those who drank the least.

Tea drinkers showed a similarly lower risk.

Decaffeinated coffee, by contrast, was not associated with any reduction in dementia risk or improved cognitive performance, suggesting that caffeine, or compounds that accompany it, is a key factor.

The Cognitive Sweet Spot

Cognitive testing added further detail.

Higher caffeinated coffee intake was linked to modestly better scores on standardized memory and thinking assessments, and fewer people in that group reported noticeable changes in their own memory (7.8% versus 9.5% among the lowest drinkers).

The most pronounced benefits appeared at approximately two to three cups of caffeinated coffee per day, or one to two cups of tea.

Beyond those levels, the advantage did not continue to grow.

Whether the mechanism involves caffeine’s influence on neuroinflammation, cerebral blood flow, or amyloid plaque buildup remains to be confirmed, but the consistency across two long-running cohorts strengthens the signal considerably.

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Adapted from Zhang Y, et al. “Coffee and Tea Intake, Dementia Risk, and Cognitive Function.” JAMA. 2025. doi:10.1001/jama.2025.27259