A major new study published in the journal JAMA has found an association between moderate consumption of caffeinated coffee and a lower risk of dementia. Researchers analysed data from 131 821 people who took part in two large American studies — the Nurses’ Health Study and the Health Professionals Follow-up Study. Follow-up continued for up to 43 years, with an average of 36,8 years.
At the start of the study, the participants had no dementia, cancer or Parkinson’s disease. During the follow-up period, dementia was diagnosed in 11 033 people.
Among people who drank caffeinated coffee more often, 141 cases of dementia were recorded per 100 000 person-years. In the group of those who drank almost no such coffee, this figure was 330 cases. After accounting for age, lifestyle, health status and other factors, the risk of dementia among avid caffeinated-coffee drinkers was approximately 18% lower.
A similar association was observed with subjective decline in memory and thinking — the kind a person notices themselves. Such complaints were reported in 7,8% people with the highest consumption of caffeinated coffee and in 9,5% of those who drank it rarely or not at all.
The association persisted in people with different genetic risks of dementia. At the same time, decaffeinated coffee showed no significant association with a lower risk. Tea was also associated with a lower risk, but the effect was weaker; the most pronounced differences were observed with the consumption of one to two cups a day.
The most notable association for caffeinated coffee was with moderate consumption — roughly two to three cups a day. With further increases in the amount, no additional reduction in risk was found. However, the authors do not call this dose “optimal” and do not recommend starting to drink coffee in order to prevent dementia.
The study is observational: it shows an association but does not prove that coffee itself protects the brain. It is possible that coffee lovers on average eat differently, move more, or have other health characteristics that also affect the risk of dementia. Nevertheless, the results are consistent with possible biological mechanisms: caffeine and polyphenols may influence inflammation, oxidative stress and the state of blood vessels.
The authors emphasise that the effect is moderate and that coffee does not replace proven measures for preventing dementia — physical activity, control of blood pressure, blood sugar and cholesterol, adequate sleep, social activity and not smoking. The question of whether a habitual morning cup of coffee can become part of a strategy for healthy brain ageing has yet to be studied.
