Alcohol and Dementia: A Tale of Two Studies | The Body of Evidence

Alcohol and Dementia: A Tale of Two Studies

Does Drinking alcohol cause dementia or prevent it?


A funny thing happened recently two studies came out within a few weeks of each other, one suggesting that alcohol causes dementia and that other saying it could prevent. Well I really couldn’t let that slide even though I was on vacation at the time. So I decided to drill down into the studies to see what they actually said. Here’s the article, you can read it here: 

http://montrealgazette.com/opinion/opinion-does-drinking-alcohol-cause-d...

 

P.S. definitely read the comments


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Recently there was a headline “Even a moderate amount of drinking could cause brain decline,” which was no doubt troubling to anyone who enjoys an evening cocktail. But just a few weeks later another headline read, “Cheers! Regular drinkers might live longer lives without dementia” and oenophiles the world over breathed a collective sigh of relief.

 

The casual reader could be forgiven for being confused as he or she ponders whether to pour a glass of wine with dinner. That health news is often contradictory is no great surprise, and the miracle of today will likely be accused of causing cancer tomorrow. But such a flip-flop on alcohol in so short a time warrants examination.


That alcohol might be beneficial was suggested by the Rancho Bernardo study. Volunteers were recruited between 1972-1974 and followed up every four years. They were asked about alcohol consumption once during the 1984-1987 visits. The study found that that those who drank alcohol, especially moderate and heavy drinkers, were more likely to make it to 85 years old and be dementia-free than those who drank no alcohol.


The study showing harm was published in the British Medical Journal (BMJ) and used the Whitehall II cohort from the United Kingdom, another decades-long cohort study, which re-interviewed subjects every five years. At each five-year interval, the patients were asked how much alcohol they drank and were given some memory tests. The new finding in this study was that 550 subjects were randomly selected to get an MRI to look for changes in the brain, particularly the hippocampus, which is involved in memory formation. They found that those who drank more alcohol had a smaller hippocampus. The results of the memory tests were inconsistent. Some showed decline, while others apparently did not.

So which is the correct study? The Ranch Bernardo study comes up short in terms of how they measured alcohol consumption, having collected that information only once in the mid-1980s. However, even the Whitehall study only gathered this information every five years. Asking someone to guestimate weekly alcohol consumption over many years is known to be unreliable.


The BMJ Whitehall study measured brain structure on MRI rather than measuring dementia in patients. While MRIs are all well and good, they don’t necessarily correlate with symptoms; and while your hippocampus may be smaller, that doesn’t mean you will get Alzheimer’s disease. In this, the Rancho Bernardo study did better by actually testing people for dementia, but they had another problem. You had to make it to 85 to have a positive outcome. If you died before your 85th birthday, as 41 per cent of subjects did, we don’t know whether you would have gone on to develop dementia. This introduces something called survivor bias and could skew the results.


In the end, neither study is perfect, but neither study is particularly bad, either. The findings are inconsistent and contradictory, but then so are most findings in nutrition research. The problem lies in news reports that fail to put new research findings in context. Few who touted the benefits of alcohol mentioned that weeks before they claimed it was harmful.


When trying to decide whether alcohol is good or bad for you, it is worth keeping this in mind: Alcohol is teratogenic (causes birth defects) and it increases your risk of cancer. If I told you that about any other food you would avoid it like the plague. When it comes to dementia, you would be hard pressed to find any clear consensus when it comes to alcohol. It remains unclear whether it is, overall, good or bad for you, but ultimately, any effect is likely to be small. The one guarantee is that if you drink enough of it, it will make you fat. After all, it’s not called beer belly for nothing.