Coffee vs. Dementia? A Massive Study Just Found a Surprising Link
Over the years, caffeine has attracted attention for its potential brain-protective effects. Now, a decades-long study of more than 131,000 people adds to that evidence, finding that people who regularly drank coffee or tea had a lower risk of developing dementia.
Daily Coffee and Tea Drinkers Have Lower Dementia Risk
Scientists have long wondered whether caffeine could help keep the brain healthy as people age. While several studies have hinted at a benefit, many were limited by short follow-up periods or only measured people’s diets once, making it difficult to understand the long-term effects. The new study, published in JAMA, analyzed data from 131,821 participants enrolled in the Nurses’ Health Study and the Health Professionals Follow-up Study, two long-running U.S. health studies.
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Over up to 43 years of follow-up, participants reported their intake of caffeinated coffee, decaffeinated coffee, and tea every two to four years. Researchers then tracked dementia diagnoses and changes in cognitive function using self-reports and, in one study group, telephone-based cognitive testing.
Overall, people who drank more caffeinated coffee or tea had a lower risk of developing dementia and slightly better cognitive outcomes. Those in the highest caffeinated coffee group had an 18% lower dementia risk than those in the lowest group. People in the highest tea group had about a 14% lower risk. The association between coffee and tea consumption and lower dementia risk was broadly similar regardless of genetic risk for Alzheimer’s disease. It was also somewhat stronger among participants aged 75 and younger, which researchers said may reflect the greater influence of lifestyle factors earlier in the disease process.
More wasn’t necessarily better, however. The researchers conducted a dose-response analysis to determine whether the relationship changed at different levels of intake. They found that the apparent benefits leveled off at moderate consumption. The analysis identified a “sweet spot.” The strongest associations were seen at about 2 to 3 cups of caffeinated coffee per day, 1 to 2 cups of tea per day, or roughly 300 milligrams of caffeine daily. Consuming more than that did not appear to provide additional benefits.
Decaffeinated coffee did not show a similar protective effect. Researchers caution that this does not necessarily mean decaf is harmful, as people who choose decaf may have underlying health conditions that influence dementia risk. People who drank more coffee and tea also reported fewer memory and thinking problems. Those with higher caffeinated coffee intake performed slightly better on cognitive tests, with results suggesting brain function comparable to someone about seven months younger.
“Caffeine might reduce the accumulation of amyloid-beta, which is a toxic protein that can be found in the plaques that are associated with Alzheimer’s disease.”
Dr. Dylan Wint, a neurologist at Cleveland Clinic
As encouraging as the findings are, the study was observational. This means it can only show an association between coffee, tea, and dementia risk. It cannot prove that caffeine directly prevents dementia. For now, the findings suggest that for people who already enjoy coffee or tea, moderate consumption may be one small part of a broader brain-healthy lifestyle.
“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. Our study suggests that caffeinated coffee or tea consumption can be one piece of that puzzle,” Dr. Daniel Wang, associate scientist at Mass General Brigham and senior author of the study, said in a news release.
How Caffeine May Help
Researchers are still working to understand exactly why caffeine may be linked to better brain health, but several biological explanations have emerged. One leading theory involves a brain chemical called adenosine, which helps regulate sleepiness and alertness. Throughout the day, adenosine gradually builds up in the brain, creating what scientists call “sleep pressure”—the growing drive to sleep that develops the longer you stay awake.
This is also how coffee helps keep you alert. Adenosine works by attaching to receptors on brain cells, much like a key fitting into a lock. When it binds to those receptors, brain activity slows down and the release of certain brain chemicals involved in attention, mood, and memory decreases. Caffeine can temporarily block some of these receptors, preventing adenosine from delivering its “time to rest” signal.
Researchers believe this same mechanism may also help explain caffeine’s potential effects on brain health. In Alzheimer’s disease, certain adenosine receptors appear to become more active.
“Caffeine might reduce the accumulation of amyloid-beta, which is a toxic protein that can be found in the plaques that are associated with Alzheimer’s disease,” said Dr. Dylan Wint, a neurologist at Cleveland Clinic.
Inflammation may also play a role. Chronic low-grade inflammation is increasingly recognized as a contributor to brain aging and neurodegeneration. Some studies suggest caffeine may help dampen inflammatory processes in the brain, potentially offering another layer of protection.
While this study points to caffeine as a likely driver of the observed benefits, coffee and tea contain other potentially beneficial compounds as well. These include polyphenols such as chlorogenic acids in coffee and catechins in tea, which have antioxidant and anti-inflammatory properties. Some studies suggest these compounds may also help protect brain cells from damage and support healthy brain aging.
Coffee and tea may also support brain health indirectly by benefiting cardiovascular and metabolic health. Conditions such as high blood pressure, diabetes, and cardiovascular disease are all known risk factors for dementia. Some research suggests moderate caffeine intake may improve aspects of vascular health and glucose metabolism, which could in turn support healthy brain aging.
Brain Health Takes More Than Your Daily Cup
Taken together, these findings suggest that coffee and tea may support brain health through multiple pathways. However, experts stress that no single food or drink can prevent dementia on its own. So while there may be another reason to savor your daily cup of coffee or tea, it’s still just one piece of the puzzle. Protecting your brain as you age requires a combination of healthy habits, from staying physically active to eating well, sleeping enough, and keeping chronic conditions under control.
