Moderate caffeinated coffee intake linked to lower dementia risk in long US cohort

Adults in a long-running US study who drank more caffeinated coffee developed dementia at a markedly lower rate than those who rarely or never drank it. The analysis, published in JAMA by Yu Zhang, Dong D. Wang and colleagues, followed participants for up to 43 years. The pattern was strongest at two to three cups a day, and it did not hold for decaffeinated coffee.

What the data show

Among people with higher caffeinated coffee intake, the researchers recorded 141 dementia cases per 100,000 people each year. For those who rarely or never drank caffeinated coffee, the figure was 330 per 100,000. Such a gap is large in relative terms, but it describes a statistical association between two groups of people, not an effect shown to result from coffee itself.

The team also looked at subjective cognitive decline, meaning memory or thinking changes that people notice themselves without necessarily having them confirmed by formal testing. It was reported by 7.8% of higher caffeinated coffee drinkers, against 9.5% of those who rarely or never drank it. This is a smaller difference, and self-reported measures are less precise than clinical diagnoses. Even so, it points in the same direction as the dementia figures.

A moderate amount, not the most

Two to three cups of caffeinated coffee a day were linked to the most favourable results for both dementia risk and cognitive function. Intake above that range did not appear to add protection, so the relationship does not look like a simple case of more being better.

The association was seen regardless of participants' genetic risk of dementia. People with an inherited predisposition showed the same broad pattern as those without. That is a useful observation for researchers, since it suggests the link is not confined to low-risk groups, although it says nothing about whether coffee alters the biology of the disease.

Tea and decaffeinated coffee

Tea drinking was also associated with lower dementia risk and better cognitive function. The strongest associations appeared at one to two cups a day, and again higher intake brought no further apparent benefit. The study did not separate caffeinated from noncaffeinated tea, so it cannot say whether caffeine accounts for the tea findings.

Decaffeinated coffee did not show the benefits seen with regular coffee. This hints that caffeine, rather than other compounds in the bean, may be involved. The authors' account, as reported, stops well short of that conclusion. Caffeinated and decaffeinated drinkers may differ in other ways, such as health status, habits or the reasons they chose decaf, and these could shape the results.

Limitations and next steps

The work is observational. It cannot show that coffee prevents dementia, and differences between coffee drinkers and abstainers could explain part of the gap. The source summary does not give the number of participants, how diet was assessed or which other factors were adjusted for, so readers will need the full paper to judge how robust the estimates are.

Several questions follow from the findings:

• Whether caffeine itself, rather than lifestyle differences, drives the association.
• Whether caffeinated and noncaffeinated tea differ in their links to cognition.
• Which biological pathways, if any, could connect regular caffeine intake to brain ageing over decades.
• Whether controlled studies or other long-term cohorts can reproduce the dose pattern, with a peak at moderate intake.

For now, the study adds a large, long-duration dataset to the literature on diet and cognitive ageing. It supports further investigation of caffeine and dementia, but it does not provide grounds for changing clinical advice.

Source: Drinking 2–3 cups of coffee a day linked to dramatically lower dementia risk (ScienceDaily: health and medicine, 7 November 2026).

Image: AI-generated illustration.