Moderate alcohol consumption can lead to cognitive decline, adverse brain outcomes
Alcohol intake, even in moderation, is a risk factor for multiple markers of abnormal brain structure and cognitive function, including hippocampal atrophy, a recent UK study has found.
“We have found a previously uncharacterized dose-dependent association between alcohol consumption … and hippocampal atrophy, as well as impaired white matter microstructure,” researchers said. “Additionally, higher alcohol consumption predicted greater decline in lexical fluency but not in semantic fluency or word recall.”
Over the 30-year follow-up, higher alcohol consumption showed a correlation in a dose-dependent manner with greater odds of hippocampal atrophy. Interestingly, even individuals who drink moderately (14 to 21 units/week) had a threefold chance of having right-sided hippocampal atrophy (odds ratio [OR], 3.4; 95 percent CI, 1.4 to 8.1; p=0.007), while those who drink more than 30 units a week had the highest risk compared with abstainers (OR, 5.8; 1.8 to 18.6; p≤0.001). [BMJ 2017;357:j2353]
“The finding that alcohol consumption in moderate quantities is associated with multiple markers of abnormal brain structure and cognitive function has important potential public health implications for a large sector of the population,” researchers said.
Light drinking (1 to <7 units/week) showed no protective effect compared to abstinence. In addition, higher alcohol consumption correlated with differences in corpus callosum microstructure and faster decline in lexical fluency, but not with cross-sectional cognitive performance or longitudinal changes in semantic fluency or word recall.
“Our findings support the recent reduction in UK safe limits and call into question the current US guidelines, which suggest that up to 24.5 units a week is safe for men, as we found increased odds of hippocampal atrophy at just 14 to 21 units a week, and we found no support for a protective effect of light consumption on brain structure,” researchers said.
“Alcohol might represent a modifiable risk factor for cognitive impairment, and primary prevention interventions targeted to later life could be too late,” they added.
The results of this study strengthen the view that the beneficial effects of alcohol on health, if any, is probably limited to low intakes of no more than a unit a day, according to Killian A Welch, consultant neuropsychiatrist at the Robert Fergusson Unit, Royal Edinburgh Hospital, UK. Nonetheless, this level of consumption still carries risk relative to abstinence for such conditions as breast cancer, and the evidence of benefit is not strong enough to justify advising abstainers to drink. [BMJ 2017;357:j2645]
“We all use rationalisations to justify persistence with behaviours not in our long-term interest,
Welch said. “With publication of this paper, justification of ‘moderate’ drinking on the grounds of brain health becomes a little harder.”
This observational cohort study involving 550 men and women (mean age 43.0 years at baseline) measured weekly alcohol intake and cognitive performance repeatedly from 1985 to 2015. At study endpoint (2012 to 2015), researchers conducted multimodal magnetic resonance imaging (MRI). Of the participants, 23 were excluded due to incomplete or poor quality imaging data or gross structural abnormality, or incomplete alcohol use, sociodemographic, health or cognitive data.
“Prospective studies of the effects of alcohol use on the brain are few, and replication of these findings in other populations will be important,” researchers said. “Investigations with larger numbers are needed to clarify whether there are graded risks between short versus long periods of higher alcohol consumption.”