Right now, more than 7 million Americans are living with Alzheimer's disease. By 2060, that number is projected to nearly double to 13.8 million people. Between 2000 and 2022, deaths from Alzheimer's disease increased by more than 142% [1].
And Alzheimer's is just one type of dementia. Taking all forms together, there are an estimated 49 million people over 65 worldwide living with dementia [2].
But currently, there's no cure for dementia, and treatment options are severely limited. Recent FDA-approved medications like donanemab show only modest benefits. They can slow the condition, not stop or reverse it. And they're very expensive and carry risks.
This is why prevention has become so crucial. If we can identify modifiable risk factors — things we can actually change in our daily lives — we might be able to delay or prevent dementia before it starts.
And that brings us to your morning coffee. Some have speculated that it might have protective effects, lowering rates of dementia. Limited evidence has pointed in that direction. But study results have been mixed, and researchers haven't been sure [3]. In this article, I'll break down what a massive new study tells us about the link between coffee and dementia risk.
Table of Contents
- The Landmark Coffee and Dementia Study
- How Coffee Protects the Brain
- Important Caveats
- Practical Takeaways
- References
The Landmark Coffee and Dementia Study
Could something as simple as your daily coffee potentially make a difference? And does caffeinated vs decaf matter? These are hard questions to answer. Dementia develops slowly over decades. To answer these questions properly, you need more than a few hundred people followed for a couple of years. You need a massive, decades-long investigation. And that's exactly what a new study gives us.
The study included 2 large cohorts with over 130,000 people. They started accumulating data for one cohort in 1980 and the other in 1986. Up to 43 years of follow-up was included in the study [4].
And here's what makes this study distinctive, in addition to its size and timeframe. The data includes frequent, repeated measures of coffee intake. Participants filled out detailed food questionnaires every 2-4 years. This captured how their habits changed over decades, giving a true picture of long-term consumption [4].
Researchers also kept an eye on multiple outcomes. They didn't just track dementia diagnoses. Instead, they measured cognitive function to look for markers of decline that could indicate early stages along the path to the disease. They did this through asking how participants felt their minds were working and also looking at scores on a cognitive performance test [4].
Finally, researchers took great pains to account for factors that could skew the results. They adjusted for multiple factors from basic demographics to lifestyle and diet quality [4].
So after analyzing all the data, here's what they found. Over the 43 years of follow-up, just over 11,000 people developed dementia [4].
And here's where it gets interesting. Researchers divided participants into four groups, depending upon the amount of coffee they regularly drank. Compared to the group that didn't drink coffee, the next highest level of intake was associated with a 2% risk reduction for developing dementia. These are people drinking less than one 8-oz cup of coffee a day. For the third group, drinking 1 to 2.5 cups a day, we see a massive reduction. Now it's 19%. Then something surprising happens. With the fourth group — those who drink the most coffee, about 2.5 to 4.5 cups a day — the risk reduction actually pulls back a little. It's 18% [4].
To put it simply, moderate coffee drinkers had about a fifth fewer dementia cases.
But it looks like coffee may have a protective effect even before a dementia diagnosis. When researchers asked people to report on their memory and thinking, they again saw a difference based on coffee intake. 9.5% of non-coffee drinkers reported noticing some cognitive problems. The share for the highest coffee consumers was 7.8%. In other words, those with the highest intakes had about a 15% lower risk than those who drank no coffee [4].
What about the objective tests of cognitive function? These tests were only done with one of the cohorts. They were in line with the rest of the data. Higher intakes of coffee were associated with better cognitive performance, but the difference was modest here [4].
Now here's the twist that tells us something crucial about why coffee might be protective. Decaffeinated coffee showed no protective effect [4].
And that raises a natural question. What about caffeinated tea? The researchers looked at that, too. And they found similar benefits, though the risk reduction was a bit weaker [4].
There's an important nuance to the data that's easy to miss. It isn't a simple matter of "the more coffee, the better." When researchers analyzed the relationship between dose and benefit, they found that benefits didn't just climb with every extra cup. There was a sweet spot at about 2 to 3 cups per day of caffeinated coffee or 1 to 2 cups a day of tea. Beyond that, benefits plateaued [4].
And the benefits were remarkably consistent across different subgroups — independent of genetic predisposition, including APOE4 genotype, and major risk factors of dementia and cognitive decline [4].
How Coffee Protects the Brain
So caffeinated coffee and tea appear to be effective in reducing dementia risk. The question is, how? What is caffeine actually doing in the brain that might protect against dementia?
As we've seen, this study suggests caffeine is the primary player. It blocks adenosine receptors in the brain, which is why it helps prevent drowsiness. But it turns out this also appears to decrease amyloid plaque formation, which is thought to be an important driver of Alzheimer's disease [4].
Caffeine has other potentially protective effects as well. It may lower inflammation in the brain. It can improve insulin sensitivity, reducing the risk of type 2 diabetes, which is a major risk factor for dementia [4].
And even though caffeine appears primary, coffee and tea contain polyphenols and other compounds that have demonstrated the ability to counter oxidative stress and improve the function of blood vessels [4].
Dementia isn't caused by just one thing; it's a cascade of problems. The exciting thing is that coffee seems to address several of them at once.
Important Caveats
But I need to mention two important caveats. First, this study was observational. So it can't definitively tell us about causation. But we're never going to see a 40-year randomized controlled trial with coffee, so this may be as close as we get. Researchers took pains to consider factors that might distort the results, but it's still possible something else is going on here, and coffee consumption isn't the real driver of the pattern found.
The second caveat is this. Just because this study suggests caffeine is an important element of the protective effect of tea and coffee, this doesn't mean the findings would translate to something like energy drinks. They have a significant caffeine dose, but they also typically include sugars or artificial sweeteners that might counteract any benefits. Presently, there are no good long-term studies of the impact of energy drinks. But there is a large U.K. Biobank study linking increased consumption of sugar-sweetened beverages with higher dementia risks — a 61% increased risk for those drinking more than one glass per day [5].
Practical Takeaways
If you already drink coffee, the evidence here suggests an optimal intake — as far as dementia risk goes — is in the range of 2-3 cups a day. And that's actually consistent with research on coffee's benefits in other areas, like heart health.
When we drink those cups is important, though. We want to avoid drinking coffee later in the day, which can disrupt sleep. That's counterproductive, since sleep is crucial for brain health. I advise my patients to finish caffeine intake within 4 hours of waking up.
And we want to watch out for additions like sugar and cream. Again, these can have negative health impacts that can counteract the benefits. In addition, we should stick to filtered coffee. Studies show that unfiltered coffee can raise LDL cholesterol.
Once more, decaf coffee doesn't seem to give the same benefits. But, of course, caffeine isn't for everyone.
If you don't drink coffee, this study doesn't necessarily mean you should start. But you might consider tea as an alternative that was associated with similar benefits in the study.
References
1. https://alz-journals.onlinelibrary.wiley.com/doi/full/10.1002/alz.70235
2. https://www.frontiersin.org/journals/publichealth/articles/10.3389/fpubh.2025.1585711/full
3. https://www.sciencedirect.com/science/article/abs/pii/S0899900715005389
4. https://jamanetwork.com/journals/jama/article-abstract/2844764
