Scientists, studying the effects of alcohol on cognitive function over 30 years have found that even moderate drinking could damage the brain. The research was undertaken by the University of Oxford and University College London and was published in the British Medical Journal, a peer-reviewed journal. The study is open access and can be read online.
The prospective cohort study recruited 550 participants who were already taking part in the Whitehall II study, which examined the relationship between socioeconomic status and cardiovascular health in civil servants and began in 1985. The scientists were particularly interested in looking at weekly alcohol intake and cognitive function over time and also looked at the brain structure of the participants at the end of the research.
From 1985 to 2012, lifestyle variables and health were measured at intervals. Alcohol consumption was included as mean consumption a week, using the averages over all the study phases. The researchers considered the participants ‘abstinent’ if the participant consumed less than one unit of alcohol a week, a ‘light drinker’ for between 1 and less than 7 units per week, ‘moderate drinking’ was if 7-13 units per week were consumed by women and up to 20 units for men and ‘unsafe drinking’ was defined by pre-2016 guidelines of 14+ units a week for women and 21+ units for men and by the newly revised UK Department of Health guidelines which suggested that 14 units per week for both men and women would be considered excessive.
Cognitive function was also assessed during every other phase, using a number of tests including semantic and lexical fluency, the Montreal cognitive assessment which checks for mild cognitive impairment, a trail making test which involves connecting dots to assess visual search speed and mental flexibility, the Hopkins verbal learning test, which involves asking a person to remember and recall a list of words, Rey-Osterrieth complex figure test which involves reproducing a complex line drawing, the Boston naming test, measuring word recall and naming and the digit substitution test which asks the person to match symbols with corresponding digits. The participants’ brain structure was also imaged using an MRI scan, checking their grey matter density, hippocampal atrophy and white matter, at the end of the study.
The study took into account the age, education, gender, social activity, blood pressure, smoking, cardiovascular history and whether using cardiovascular drugs of the participants. These were assessed by using a questionnaire. The scientists also asked about social class, the lifetime history of major depression and drug use.
The median alcohol consumption was 6.4 units for women and 11.5 units for men. These two numbers remained fairly constant throughout the study. Light drinkers (>7 units) showed no difference in brain structure when compared to those who abstained. The brain scans showed that higher alcohol consumption was associated with increased risks of degeneration of the hippocampus, which is associated with memory. The more alcohol that was consumed, the more degeneration was seen. Those drinking more than 30 units a week were five times more at risk from hippocampal atrophy when compared with those who abstained. Moderate drinkers (14-20 units) were three times more at risk than people who abstained. Women who drank alcohol moderately showed no significant difference to abstainers, but male moderate drinkers did.
The scientists suggested that, according to their results, a moderate consumption of alcohol could be associated with abnormalities of brain structure and therefore impaired cognitive function. This finding could have important potential public health implications for the population. They felt that the findings of this study supported the recent changes to safe limits and suggested that the US might need to review their guidelines which state up to 24.5 units a week is safe consumption limits for men. This study found that 14-21 units a week could increase the risk of impaired cognitive function. This study did not find any evidence that there might be a protection of the brain through light consumption of alcohol.
The long period of time in which this study took place means that the results cannot be ignored, as it shows changes in cognitive function over the course of the study. The participants were civil servants from the 1980s, who were mostly middle class and male, with higher IQs which may make it difficult to apply the results to the general population of the UK. There was a lower sample of women taking part and few of them drank to excess which may account for the lack of damage to the hippocampus in women. The participants self-reported their alcohol intake, which may lead to incorrect reporting. The participants only underwent one MRI scan, which did not allow the scientists to know when the brain structure changes took place and there may have been other co-founding factors which influenced cognitive impairment rather than alcohol consumption.
The likelihood is that consuming alcohol regularly, at whatever level is not good for our brains, so it is still recommended that both men and women do not consume more than 14 units in a week.
Topiwala A., et al. Moderate alcohol consumption as risk factor for adverse brain outcomes and cognitive decline: longitudinal cohort study, British Medical Journal, June 2017