The Study
A longitudinal cohort study demonstrating the beneficial effect of moderate consumption of green tea and coffee on the prevention of dementia: The JPHC Saku Mental Health Study
This study watched a group of people for many years and noticed that those who drank a few cups of green tea or coffee every day were less likely to have memory problems later. But it didn’t make them drink it — so we don’t know if the drinks caused the better memory or if those people just had healthier habits overall.
Analysis score
Maximum 72 for a cohort study.
Where the score came from
This study looked at whether drinking green tea or coffee over many years helps older people keep their memory and thinking skills.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 552 / 100
Quality score
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes — for middle-aged people, moderate tea and coffee may help protect the brain later in life, especially for men and older adults.
- 2People who drank 2–3 cups of green tea a day had 44% less cognitive decline, especially men.
- 3People who drank 1+ cups of coffee a day and were already 53+ had 46% less decline.
- 4But drinking 4+ cups of green tea didn't help.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Journal of Alzheimer's Disease
Year
2025
Authors
Akihiro Koreki, Shoko Nozaki, Ryo Shikimoto, S. Tsugane, Masaru Mimura, N. Sawada
Related Content
Claims (5)
People who drink 1 to 2.5 cups of coffee per day have a 19% lower rate of developing dementia compared to those who drink less or none.
Middle-aged adults who drink two to three cups of green tea daily have a 44% lower risk of cognitive decline over 20 years, with a stronger association observed in males.
People aged 53 and older who drink one or more cups of coffee per day have a 46% lower rate of cognitive decline over 20 years compared to those who drink less, according to a long-term study of Japanese adults.
In a study of Japanese adults, people who drank moderate amounts of green tea showed less cognitive decline over time, and this effect was greater in men than in women.
Drinking four or more cups of green tea daily does not lower the risk of cognitive decline in middle-aged adults.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.