Tea & Caffeinated Coffee are Linked to Lower Dementia Risk in a New Study
Could drinking tea help stave off dementia? A recent study looking at coffee and tea consumption over a long time scale suggests that it might. But as with all observational studies, more work is needed to understand the exact relationship between drinking tea and any health outcome.
New research supports a link between caffeine intake and lower dementia risk
This study was conducted by researchers at Harvard University and used data from more than 130,000 people who participated in follow-up studies for more than 40 years. The researchers set out to answer the question: does drinking caffeinated coffee and/or tea lower the risk of developing dementia? The main result was that either drinking caffeinated coffee (2 - 3 cups per day) or tea (1 - 2 cups per day) is associated with significantly lower dementia risk. Specifically, drinking moderate amounts of caffeinated coffee (compared to virtually no caffeine consumption) reduced overall dementia risk by about 20%. Moderate tea consumption reduced the risk by about 15%. In contrast, there was no effect from drinking decaffeinated coffee.
Importantly, they found that drinking even more coffee or tea doesn’t amplify the effect. While I would never discourage you from drinking more tea, it looks like sticking to a moderate level of tea drinking has the most potential for reducing your risk of dementia.
The bottom line? This research supports the conclusion that moderate drinking of tea or caffeinated coffee has a potential protective effect against dementia.
If you don’t drink caffeine, you don’t need to start now
I think this is important to say because often people feel like they need to change their lifestyle or habits based on research like this. But keep in mind that the results are an average effect over a large number of people. This research can’t tell you anything about your individual risk or how your body will react to caffeine. You should always consult your doctor before making any significant changes to your diet.
What makes this study different?
There have been many different studies over the years looking at links between dementia or related disorders and consumption of coffee, caffeine, and/or tea. But this is the first study to look at these links over a long period of time and in a large number of individuals. More than 130,000 nurses and other healthcare workers were followed for over 40 years as part of larger research studies. Larger studies like this have a better chance of finding results that stand up over time.
Importantly, this was also one of only a few studies that specifically looked at the effects of caffeinated vs decaffeinated coffee. The findings make sense in light of other studies that have found a positive effect of caffeine intake on cognitive function.
So what’s the catch?
I think the most important thing to keep in mind is that this study was not designed to find cause-and-effect relationships. Observational studies like these are important in picking out patterns, but other types of research – like animal studies or randomized controlled studies – are needed to see if there is a direct link between drinking caffeine and protecting against dementia. Think of this study as a clue-finding expedition. Now that we have a strong reason to suspect caffeine could be beneficial in preventing dementia, we can really start to dig into how that might work on a biological level.
Second, while this study differentiated between caffeinated and de-caffeinated coffee, it unfortunately just lumped all tea together in one category. So while it’s likely that caffeinated tea in particular is protective against dementia, we can’t tell based on these results. The study also doesn’t tell us anything about other components of coffee or tea that could be involved (like L-theanine in tea).
Finally, with large-scale cohort studies like this, there are always many caveats. The most important one in my opinion is that all of the measurements of coffee and tea consumption are self-reported. This is actually a caveat with basically all nutrition research, so nothing against this study in particular. However, the results may be slightly more reliable in the study groups used here compared to the general population, since all of the study participants worked in healthcare.
I did want to note that I was pleasantly surprised with the popular reporting of this study in the media. Even though there were a few overhyped headlines out there, the articles themselves did a fantastic job overall of reporting the results accurately and clearly. Here are a few that you might want to check out:
The New York Times: https://www.nytimes.com/2026/02/09/health/coffee-tea-dementia-risk.html
Alzheimer’s Research UK: https://www.alzheimersresearchuk.org/news/could-tea-or-coffee-reduce-dementia-risk-heres-what-you-need-to-know/
NBC News: https://www.nbcnews.com/health/health-news/coffee-benefits-dementia-risk-lower-tea-benefits-two-three-cups-rcna257853 (great article, despite the headline)
In case you want more detail
This discovery in this study was made by analyzing data from two long-term studies that started more than 40 years ago. The first followed more than 120,000 female nurses beginning in 1976; the second followed over 50,000 male health professionals beginning in 1986. Many different health and lifestyle factors were measured over the course of these studies until 2023 – consumption of caffeinated coffee, decaffeinated coffee, and tea were among them. Every few years, the study participants were asked to fill out questionnaires or take other tests so that researchers could eventually use the data to learn more about specific disease outcomes, including Alzheimer’s Disease and other forms of dementia and cognitive decline. It's also important to note that this was a prospective cohort study, meaning that the study questions (eg, “does drinking tea lower risk of Alzheimer’s Disease?”) were decided on before any measurements were taken. This makes the statistical analyses more likely to pick up true associations, compared to retrospective studies.
After adjusting for different things that could potentially skew the results (like genetic predisposition to Alzheimer’s or lifestyle factors such as smoking or drinking alcohol), they were able to show a strong effect of both caffeinated coffee and tea on lowering the risk of dementia. The results from other subjective measures of cognitive function weren’t as strong. That’s not surprising, since those data are inherently noisier.