Tea — Not Proven To ‘Protect You Against Dementia’

“It’s tea time! How at least two cups a day can shield you from dementia,” reports the Mail Online. This rather optimistic headline reports on a Singaporean study of around 900 Chinese people aged 55 and above.

The study searched for a potential link between tea consumption and development of dementia. It found the risks of dementia were halved in tea-drinkers. However, when breaking the results down further, the links were only significant for women who drank three to four cups a day and in drinkers who carry a particular dementia-risk gene.

Despite the relatively large sample size, only 72 people developed dementia. But breaking down this number further according to tea intake leaves only small groups for analysis. And the smaller the sample size, the bigger the risk that pure chance affected the results.

Also, despite adjusting for other health and lifestyle factors that could be influencing the link, it is always difficult to isolate the direct effect of tea drinking.

The researchers suggest that promotion of tea drinking could have benefits for the brain but they also point out that further studies are needed to confirm the results found in their study.

There is currently no guaranteed method(s) of preventing dementia, but a useful maxim is “what is good for the heart is also good for the brain”. Regular exercise, a healthy diet, moderate alcohol consumption and avoiding smoking can help lower dementia risk.

The study was carried out by researchers from the National University of Singapore. It was funded by the Biomedical Research Council; the Agency for Science, Technology and Research; the Virtual Institute for the Study of Ageing; and the Alice Lim Memorial Fund.

The study was published in the peer-reviewed Journal of Nutrition, Health and Aging.

The Mail Online’s headline was overly optimistic: it took the 50% figure at face value. The website noted the small sample size, but the limitations of the study were not discussed.

In Chinese culture, the consumption of strong tea is considered to enhance brain-based skills such as memory and alertness in the short-term. However, the regular consumption is also thought to have long-term benefits, which several studies have previously looked into.

With this background, the authors of this research wanted to further test the hypothesis that tea drinkers are less likely to develop brain disorders such as dementia, when compared to non-drinkers.

The researchers also wanted to see whether the association was different between males and females, and in people carrying a high-risk variant of the apolipoprotein (APOE) gene – studies have suggested that people are more likely to develop Alzheimer’s if they carry this gene type.

Cohort studies are valuable for testing the association between an exposure and outcome, and although they aren’t always able to prove cause and effect, can give a good indication of any potential links.

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