Harvard Study: Two to Three Cups of Coffee Daily Linked to 18% Lower Dementia Risk

That morning cup of coffee might be doing more than waking you up. A major new study from Harvard researchers has found that drinking two to three cups of caffeinated coffee daily is associated with an 18 percent lower risk of dementia compared to minimal consumption.

The research, published February 9 in JAMA (Journal of the American Medical Association), tracked 131,821 participants over up to 43 years, making it one of the most comprehensive studies on coffee and cognitive health to date.

The Numbers

Of the 130,000-plus participants, 11,033 eventually developed dementia. Those who drank the most caffeinated coffee showed notably better outcomes:

• 18% lower dementia risk compared to minimal coffee drinkers
• Lower subjective cognitive decline (7.8% vs 9.5% in non-drinkers)
• Better performance on objective cognitive function tests

Tea drinkers saw benefits too—those consuming 1-2 cups daily showed a 14% lower dementia risk than non-drinkers.

Why Caffeine Matters

Here’s the interesting part: decaffeinated coffee didn’t show the same protective effects. This suggests caffeine itself may be the active neuroprotective agent, though the researchers note that coffee and tea contain other beneficial compounds like polyphenols that reduce inflammation and cellular damage.

“The effect size is small and there are lots of important ways to protect cognitive function as we age,” said Daniel Wang, senior author and associate scientist at Mass General Brigham’s Channing Division of Network Medicine.

Decades of Data

The research team, led by Yu Zhang, a student at Harvard Chan School, drew on two decades-long health studies—the Nurses’ Health Study and the Health Professionals Follow-up Study. These datasets provided something previous research lacked: repeated dietary assessments over extended periods, allowing researchers to track coffee habits alongside cognitive outcomes over an entire career and into retirement.

The methodology let the team distinguish between early cognitive changes and clinically diagnosed dementia, painting a clearer picture of coffee’s long-term effects.

What This Means for Coffee Drinkers

Before you double your espresso order, a few caveats. This is an observational study—it shows association, not causation. People who drink moderate amounts of coffee might share other lifestyle factors that protect cognition.

And “moderate” is the operative word here. The sweet spot appears to be 2-3 cups of caffeinated coffee or 1-2 cups of tea daily. More isn’t necessarily better.

Still, for the millions of people who already enjoy their daily coffee ritual, this is reassuring news. Your morning brew might be protecting your brain while it sharpens your focus—not a bad deal for something that tastes this good.