Fez — A daily coffee or tea habit may help lower the risk of dementia later in life, according to a large long-term study published in JAMA and summarized this week by ScienceDaily.
The study followed 131,821 US nurses and health professionals for as long as 43 years, tracking their consumption of caffeinated coffee, decaffeinated coffee, and tea alongside later cognitive health outcomes. Researchers found that higher intake of caffeinated coffee and tea was associated with a lower risk of dementia and slightly better cognitive function, with the strongest pattern appearing at moderate levels.
The findings do not prove that coffee or tea directly prevents dementia. They show an association, meaning people who drank moderate amounts of caffeinated beverages had better outcomes than those who consumed little or none.
The apparent sweet spot
Researchers reported that the most favorable results appeared among people who drank around two to three cups of caffeinated coffee a day, or one to two cups of tea. ScienceDaily reported that adults aged 75 and younger who consumed roughly 250 to 300 milligrams of caffeine daily had up to a 35% lower dementia risk.
The benefit appeared to level off beyond that point. In other words, adding more cups did not translate into greater protection.
That detail matters because excessive caffeine can affect sleep, increase anxiety, and cause discomfort in some people. Poor sleep and cardiovascular problems are themselves linked to cognitive decline, making moderation central to how scientists interpret the findings.
Why caffeine may matter
Scientists believe caffeine could support brain health through several biological pathways. It blocks adenosine, a chemical that slows brain activity, and may help maintain neurotransmitters involved in attention, memory, and alertness.
Coffee and tea also contain compounds beyond caffeine, including antioxidants and polyphenols. These may help reduce inflammation, support blood vessel health, and improve metabolic function, all of which are relevant to aging brains.
The study found no similar protective association for decaffeinated coffee. Researchers cautioned, however, that this does not necessarily mean decaf is harmful. Some people may switch to decaf because of sleep issues, blood pressure concerns, or heart rhythm problems, which can also influence dementia risk.
A cautious health message
Experts have stressed that coffee should not be treated as a standalone dementia prevention strategy. Reuters reported that the researchers framed caffeine as one possible factor within a broader healthy lifestyle, which also includes exercise, a balanced diet, good sleep, and medical care for cardiovascular risk factors.
The study also has limits. Its participants were health professionals in the United States, and their habits may not reflect broader populations. Researchers also could not fully account for differences in brewing methods, cup sizes, tea types, roast levels, or caffeine concentration.
