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Tea Will Not Protect Against Dementia

Tea lovers were probably delighted to read last week how two cups of tea per day can protect older people against the effects of dementia. The Daily Mail led the story but they were not the only news outlet to run it. Unfortunately, the reality is far from the sensational claims and NHS bosses felt compelled to correct this misinformation.

What did the Mail’s Story Claim?

According to The Daily Mail last week, a study in Singapore examined 900 older people on the effects of tea consumption. It claimed that dementia was “halved” in tea drinkers. It’s understandable why people might feel this is impressive, especially with such a large sample size, but there are significant problems with how The Daily Mail’s reported the findings. As with any newspaper’s science reporting, readers should not take these claims at face value. A deeper analysis (and some understanding of the scientific process in such studies) demonstrates the flaws.

TeaWhy This Report is Flawed

The result was technically true, but as with everything, the reality is much more complicated than the sensational (and simplistic) headline suggests. Looking deeper into the report, it seems the claim is only true for women, and only those who fit several criteria:

  • The woman in question must have the genetic marker for a certain type of dementia
  • She must also drink 4-5 cups per day to register any benefit of dementia risk reduction
  • Even then, the risk reduction is minimal

Yet that still does not take into account for the fact that little account was taken of other lifestyle factors. 72 of those studied developed dementia. Despite initial impressions of a large sample size, this is not enough to get an accurate understanding of the potential effects of tea on reducing dementia risk. With so few cases, it’s hard to ascertain the cause. The smaller a sample size is, the greater the chance there is for anomalies to appear significant. It is this issue that journalists and the media, in general, fail to grasp.

The Study’s Results

Of the 957 participants, 660 were reported as tea drinkers. Of those 660, 39 developed dementia. For the non-tea drinkers (297 individuals), 33 developed dementia. Looking at this crude and basic statistic it is understandable why the media jumped on the assumption that drinking tea could “halve” the dementia risk.

However, as already discussed, this did not take into account quantities, gender, genetics, age or other lifestyle issues of any of those involved in the study. Further analysis revealed that the results were not as statistically significant as they would appear at first glance. There are known cognitive benefits to drinking tea, but claiming that it can “protect” against dementia is dangerously flawed. Also, the study was of people of Chinese ethnicity. It cannot be assumed that what is significant for one ethnic group will apply elsewhere.

How to Evaluate a Newspaper Report

All newspapers have come in for criticism in recent years for sensationalist reporting – The Daily Mail is not alone on that issue. You don’t need to be a scientist or have a scientific education to examine and critically evaluate such claims.

  • Firstly, do not take the report at face value. Read through the article and make a note of key findings
  • The internet is a useful search resource. However, ensure you use only credible sources. A press release is more reliable than a newspaper article, but the study itself is the most reliable of all. Academic critiques can highlight flaws
  • When it comes to medical claims, the NHS website is often a good source to explain such stories in layman’s terms
  • Most studies are not open access (meaning freely available for anybody to read), but where it is, you should try to read it. The abstract and the conclusion will often provide enough information
  • Also read critiques (contained alongside the paper) as these are from experts who will spot problems