Is there really a level at which alcohol benefits cognition?

  • A very large study of adults aged 40-73 found evidence that alcohol's suggested benefit for cognition applies to a much lower level of alcohol consumption than previously claimed — only one drink a day.
  • Another longitudinal study that also removed the bias that's thought to come from including non-drinkers in the analysis, found no evidence for any cognitive benefits at any level of alcohol consumption.

Large study shows level of beneficial alcohol consumption much lower than thought

A UK study using data from 13,342 middle-aged and older adults (40-73) has found that having up to one standard unit of alcohol a day improved reaction time, but more than that amount harmed cognitive performance. The effect was more pronounced in older adults.

While several studies have suggested a U-shaped relationship between alcohol and cognition, with light to moderate consumption being beneficial to older adults, this has been quite controversial, with little consensus on how much is too much.

This study uses data from the over half a million people who participated in the UK Biobank prospective cohort study. Of these, 20,346 undertook a repeat assessment 5 years after the initial assessment. The study excluded any who disclosed a history of neurological disorder, and then included only those who consumed alcohol at least once a week. Weekly drinkers had lower levels of socioeconomic deprivation, were more likely to hold a university degree, and to be male.

Cognitive performance was assessed very simply, using a 'stop-go' reaction time task. RT decreased as alcohol consumption increased up to 10g/day, and then increased after that point. This harmful effect became stronger as people got older.

This level of 10 g/day is markedly lower than that suggested by other studies, which have variously argued for: up to 40g for women and 80g for men; up to 34g for middle-aged adults; no more than 16g.

The study omitted people who didn't drink at all, because of the 'sick quitter' effect — it's been argued that the apparent connection between moderate alcohol consumption and better health and cognition is due to bias in the control group, with many people abstaining or quitting due to health issues, and this has been supported by some recent studies. For example, a 2016 review and meta-analysis found no significant difference in mortality for low-volume drinkers once abstainer biases were adjusted for.

The main takeaway from this study — which seems quite robust given the scale of the study — is that the level of 'positive' alcohol consumption is much lower than previously claimed.

The study is open access, and can be read in its entirety at https://academic.oup.com/jpubhealth/article/40/2/304/4793394

Study shows no benefits from alcohol consumption once abstainer bias accounted for

Another longitudinal study, using a subset of participants in the Swedish Twin Registry, found no evidence for any cognitive benefits at any level of alcohol consumption.

Participants were those 486 individuals who had been surveyed on their alcohol intake in their midlife (in 1967), and also taken part in cognitive assessments 25 years later. Cognitive tests occurred at 2-year intervals for the next 10 years.

The study found a significant negative dose-response association between alcohol intake in midlife and performance on the MMSE and tests of episodic memory. There was no significant association with semantic memory and spatial ability.

As with the other study, in order to remove abstainer bias, non-drinkers were excluded from the analysis. There were 181 non-drinkers, and this group were more likely to be women, to have less education, lower socioeconomic status, higher BMI, and were more likely to have diabetes and hypertension. They did indeed perform worse on all cognitive tests, but as you can see, most of the characteristics of this group do lend themselves to such a result.

Midlife alcohol consumption was used because it was assumed that this would give a better reflection of lifetime habits than that reported in old age. As it happened, there were no heavy drinkers in the cohort — the highest consumption was 15 units/week. In this study, 1 unit corresponded to 12g.

The study is open access, and can be read in its entirety at https://www.frontiersin.org/articles/10.3389/fnagi.2018.00081/full

Reference: 

Giovanni Piumatti, Simon C Moore, Damon M Berridge, Chinmoy Sarkar, John Gallacher, The relationship between alcohol use and long-term cognitive decline in middle and late life: a longitudinal analysis using UK Biobank, Journal of Public Health, Volume 40, Issue 2, June 2018, Pages 304–311, https://doi.org/10.1093/pubmed/fdx186

Hassing, L. B. (2018). Light Alcohol Consumption Does Not Protect Cognitive Function: A Longitudinal Prospective Study. Frontiers in Aging Neuroscience, 10. https://doi.org/10.3389/fnagi.2018.00081

 

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