Recent headlines suggest that drinking, even in moderation, can damage the brain. But the data doesn’t support the claim.
Researchers from the University of Oxford and University College London asked 550 volunteers to track their alcohol intake over a period of 30 years.
There are two problems here. Firstly, ‘a self-selecting population is more likely to be healthier as it’s being observed,’ as our expert puts it.
Secondly, moderate drinkers underestimate their alcohol consumption by as much as a third according to one estimate. ‘The alcohol consumption data is entirely based on self-reported information, which is often unreliable.’
Brain structure was analysed using MRI scans, taken at the end of the 30 year study period. It was found that those who reported moderate alcohol intake (between 14 and 21 units a week) were almost twice as likely to have ‘hippocampal atrophy’ or a shrunken hippocampus. This major component of the brain assists with the formation of long-term memories.
However, the approach was inconsistent, as our expert explains: ‘Although the authors used an automated approach to assess brain structure from the MRI scans, clearly scanners and sequences change over time, so comparing longitudinal images is potentially a confounding variable.’
The researchers say the study supports the recent government recommendation to reduce alcohol intake. Both men and women are told to drink no more than 14 units of alcohol a week, or seven standard ‘small’ glasses of wine.
The study, which has been published in the British Medical Journal, doesn’t prove that moderate drinkers are damaging their brains. Our expert takes issue with the source data, among other things: ‘There are plenty of limitations here. Over 80 per cent of the cohort were men, over 70 per cent were married, over 60 per cent were in social class 1, spent a mean of 14 years in full time education and over 90 per cent were non-smokers. It’s hardly representative of the UK population at large and this limits the applicability of the findings.’
This was a study of 550 UK men and women with a mean age of 43, which followed them up over 30 years, from 1985 to 2015, to see what impact alcohol has on brain structure and function. Is it important to stress that none of the adults were alcohol dependent at baseline. At the end of the study, between 2012 and 2015, the men and women all had MRI scans to assess ageing of the brain, along with cognitive performance tests.
The important finding is that even in those who drunk alcohol in what we consider to be moderation (within the recommend limits of 14 to 21 units per week) had three times the likelihood of specific parts of their brain ageing and there was no protective effect of drinking a small amount (1 to 7 units per week). However, there was no association with alcohol consumption and brain function, such as word recall or fluency.
I think overall this is an academically interesting study, but it lacks real world validity, not just in terms of the population assessed but also the findings. Structure does not always correlate with function, as the authors found. So despite the claims, the jury is still out as to whether drinking in moderation causes hinders or harms cognitive health in the long-term.