Moderate Caffeine Intake Linked to Lower Dementia Risk and Slower Cognitive Decline

Fresh evidence adds to the growing body of research indicating that there may be no need to feel guilty about a daily coffee. A large study conducted over the long term has linked moderate caffeine intake with a lower risk of dementia and a slower rate of cognitive decline.

The researchers assessed information from almost 132,000 people who were monitored for as long as 43 years. Participants with the highest reported caffeine intake had an 18 percent lower risk of developing dementia than those who consumed little or no caffeine.

In a subgroup of participants, people who drank caffeinated coffee or tea achieved marginally higher scores in cognitive assessments than those with lower consumption. Notably, the same association was not seen among decaffeinated drinkers, pointing to caffeine itself as the potentially protective element.

Moderate caffeine intake and dementia risk

This does not mean that drinking vast quantities of coffee each day will keep the mind sharp indefinitely. As with many things, moderation matters: the strongest cognitive benefits in the study were seen in people drinking two to three cups of coffee or one to two cups of tea a day.

Even so, moderate caffeine consumption is not a cure-all.

"While our results are encouraging, it's important to remember that the effect size is small and there are lots of important ways to protect cognitive function as we age," says Daniel Wang, a nutritionist at Mass General Brigham in Boston.

"Our study suggests that caffeinated coffee or tea consumption can be one piece of that puzzle."

The findings are consistent with several recent studies. Research involving more than 200,000 people in the UK Biobank found that coffee drinkers were 34 percent less likely to develop Alzheimer's, and 37 percent less likely to develop Parkinson's, than people who did not drink coffee – provided it was caffeinated and unsweetened.

A separate study associated three cups of coffee a day with an average lifespan increase of almost two years. Another found that, among people with high blood pressure, those drinking four to five cups of tea daily had the lowest risk of developing dementia.

How the caffeine study was conducted

The latest research examined health data from 86,606 women in the Nurses' Health Study and 45,215 men in the Health Professionals Follow-up Study. Both studies started gathering data in the 1980s.

Caffeine consumption was estimated through food-frequency questionnaires completed every two to four years. Participants also reported any changes they noticed in memory, attention and other cognitive abilities. Around 17,000 people took telephone-based cognitive-function tests on several occasions throughout the study period.

Of the 131,821 participants overall, 11,033 developed dementia during the study. This corresponded to an 18 percent lower dementia risk among those in the highest caffeine-intake group compared with those in the lowest group.

People who consumed caffeinated coffee also showed a slightly lower rate of self-reported cognitive decline: 7.8 percent, versus 9.5 percent among non-coffee drinkers.

However, there was no significant difference in combined brain-function scores among participants who completed the cognitive tests.

Higher intake did not add further benefits

Interestingly, greater caffeine intake was not associated with adverse effects. Rather, the benefits appeared to plateau, meaning high intake produced broadly the same benefits as moderate consumption.

That differs from other research, which has linked drinking more than six cups a day to an increased risk of dementia.

As always, an observational study of this kind can identify associations, but cannot prove conclusively that coffee drinking lowers the risk of dementia.

In their analysis, the researchers adjusted for other lifestyle influences, including diet and medical and family history. Further research is nevertheless required to explore possible relationships between caffeine and dementia, as well as the mechanisms that may be involved.

"We also compared people with different genetic predispositions to developing dementia and saw the same results – meaning coffee or caffeine is likely equally beneficial for people with high and low genetic risk of developing dementia," adds Yu Zhang, lead author of the study.

The research was published in JAMA.