A 30-year study has found that even moderate alcohol consumption can lead to impaired brain function
In The BMJ study published this week, led by University of Oxford researchers, more than 500 British men and women had their weekly alcohol intake and cognitive performance measured repeatedly over 30 years (1985-2015).
None of the participants were considered alcohol dependent and were categorised according to alcohol consumption levels:
- ≥30 units a week (High consumption)
- 21-<30 units a week (High consumption)
- 14-<21 units a week (Moderate consumption)
- 7-<14 units a week (Moderate consumption)
- 1-<7 units a week (Light consumption)
- 0-<1 units a week (Abstainers)
Cognitive function of participants was assessed at several points throughout the study, through a variety of tests including lexical and semantic fluency tests; short-term memory recall tests; trail making tests; figure tests; verbal learning tests; naming tests; digit substitution tests; and more.
Their brains were also scanned using MRI at the end of the study (between 2012 and 2015).
Higher alcohol consumption over the 30-year follow-up period was associated with increased odds of hippocampal atrophy (loss of brain volume/degeneration of the brain cells in the hippocampus).
The hippocampus is a part of the brain associated with memory, space and emotions, and is one of the areas that Alzheimer’s disease – the leading cause of dementia and memory loss – attacks first.
Those consuming over 30 units a week were at the highest risk of hippocampal atrophy compared to abstainers (odds ratio 5.8, 95% confidence interval 1.8 to 18.6; P≤0.001).
And even participants drinking moderately (14-21 units a week) had three times the odds of right-sided hippocampal atrophy compared with abstainers (P=0.007).
Average alcohol consumption over the study (units/week) was negatively correlated with grey matter density, especially in hippocampus and extending anteriorly into the amygdalae, even after adjustment for multiple potential confounders.
Higher alcohol use was associated with differences in the brain’s corpus callosum (white matter) microstructure – an area that facilitates communication between the two sides of the brain.
Those drinking at moderate-to-high levels of consumption were also found to decline faster in their lexical (i.e. vocabulary) scores compared to abstainers (P=0.006).
This effect was independent of age, sex, IQ, education, social class, and stroke risk score.
There was also no evidence to support light drinkers were relatively protected from either cognitive decline or hippocampal atrophy compared with abstainers.
The finding that alcohol consumption even in moderate quantities is associated with multiple markers of abnormal brain structure and cognitive function “has important potential public health implications,” say the researchers, led by Dr Anya Topiwala from the University of Oxford’s Department of Psychiatry.
Alcohol dependence has been already established as a major cause of dementia, while even light drinking has been associated with increased risk of cancers of the oesophagus, breast and oropharynx.
Epidemiological studies have often reported better health in moderate drinkers compared with abstainers, but these results show otherwise, says neuropsychiatrist Dr Killian Welch who specialises in brain injury rehabilitation and substance misuse in Edinburgh, UK.
“[This paper] strengthens the view that if alcohol does confer beneficial effects on health, the link is probably confined to low intakes of no more than a unit a day,” says Dr Welch in an accompanying BMJ editorial.
“Even this level of consumption carries risk relative to abstinence for conditions such as breast cancer, and the evidence of benefit is certainly not strong enough to justify advising abstainers to drink.”
He warns that widespread alcohol consumption may lead to health and financial crises in the future due to increased rates of dementia and brain damage across the population.
“With increasing longevity, maintenance of brain health into older age is a key priority of our time. Leaving aside the human cost of dementia, care of cognitively impaired older people is a looming financial crisis,” says Dr Welch.
“As intake increases, so does the risk to health, probably in a dose-dependent manner.
“We all use rationalisations to justify persistence with behaviours not in our long-term interest. With publication of this paper, justification of ‘moderate’ drinking on the grounds of brain health becomes a little harder.”