Coffee and Tea Linked to 18% Lower Dementia Risk

A 43-Year Study Points to Coffee's Brain Benefits

Your morning cup of coffee may be doing more than just waking you up. A sweeping study tracking over 131,000 people for up to 43 years has found that moderate consumption of caffeinated coffee or tea is associated with an 18 percent lower risk of developing dementia — and measurably better cognitive performance over time.

The research, published in JAMA, drew on data from the Nurses' Health Study and the Health Professionals Follow-Up Study, two of the longest-running health investigations in the world. Led by researchers at Harvard, Mass General Brigham, and the Broad Institute of MIT and Harvard, it represents one of the most robust examinations of caffeine's relationship with brain health to date.

The Sweet Spot: Two to Three Cups a Day

Among the 131,821 participants — followed from 1980 through 2023 — 11,033 developed dementia. Those who drank two to three cups of caffeinated coffee daily (roughly 300 milligrams of caffeine) had the lowest risk. Tea drinkers weren't far behind: consuming one to two cups daily was associated with a 14 percent reduction in dementia risk.

Coffee drinkers also reported lower rates of subjective cognitive decline — 7.8 percent compared with 9.5 percent among non-drinkers — and performed better on objective cognitive tests. Crucially, these benefits held regardless of participants' genetic predisposition to Alzheimer's disease.

Decaffeinated coffee, however, showed no protective effect, suggesting caffeine itself plays a central mechanistic role.

Why Caffeine May Protect the Brain

Scientists point to several bioactive compounds in coffee and tea that could explain the findings. Polyphenols, particularly chlorogenic acids and caffeic acid, possess potent antioxidant and anti-inflammatory properties. Trigonelline, an alkaloid found in coffee, has been shown in laboratory studies to suppress neuroinflammation, modulate neurotransmitter release, and support mitochondrial function — all factors relevant to neuroprotection against age-related cognitive decline.

"We are not recommending that people who don't drink coffee start drinking," cautioned lead researcher Dr. Yu Zhang of Harvard's T.H. Chan School of Public Health. "We are just seeing that for people who already drink coffee, the results are really reassuring."

A Growing Global Crisis

The findings carry particular urgency given the scale of the global dementia challenge. According to the World Health Organization, more than 55 million people currently live with dementia worldwide — a figure projected to surge past 150 million by 2050 as populations age, with the steepest increases expected in low- and middle-income countries.

Any modifiable lifestyle factor that could meaningfully reduce risk — even modestly — represents a significant public health opportunity.

Important Caveats

Senior author Dr. Daniel Wang of Mass General Brigham stressed that "the effect size is small" and that coffee consumption is just one piece of a broader dementia prevention strategy that includes physical activity, social engagement, and cardiovascular health management.

The study also has limitations. It did not differentiate between types of tea, did not account for coffee preparation methods or added sweeteners, and relied partly on self-reported consumption data. The protective association was stronger among participants under 75, suggesting timing of consumption may matter.

Still, for the billions of people worldwide who reach for a cup of coffee or tea each morning, the message is encouraging: that daily ritual may be quietly safeguarding the brain, one sip at a time.