"Individuals with a poor ability to process alcohol did indeed suffer a cognitive decline if they drunk more alcohol. But individuals with a good ability to process alcohol actually showed the reverse effect."
A new study from the University of Edinburgh uses an unique longitudinal dataset - the Lothian Birth Cohort - and an ingenious analysis technique called Mendelian Randomisation to disentangle the causal influence of drinking alcohol on cognitive change in older age.
The Lothian Birth Cohort consists of Scots born in 1936 studied during the Scottish Mental Survey of 1947 and then between 2004 and 2007 when Professor Ian Deary of the University of Edinburgh followed up participants in the original survey. The data these participants provided included an IQ test at around the age of 11 and another at around the age of 70. Importantly, possible confounds on IQ test score such as socioeconomic status and education were also recorded, as well as a measure of alcohol consumption (at the age of 70, 'over the past few months').
The neatest part of the study, however, was to look at the influence of genetics on the effects of alcohol. Certain rare genetic variants are known to be related to the body's ability to process alcohol. Individuals with more of these variants are worse at processing alcohol and so, for a given amount of alcohol consumption, will have higher exposure to the potentially damaging effects of alcohol. The analysis, led by Dr Stuart Richie, showed that individuals with a poor ability to process alcohol did indeed suffer a cognitive decline if they drunk more alcohol. But individuals with a good ability to process alcohol actually showed the reverse effect – for these individuals, higher alcohol consumption predicted actual improvements in cognitive ability.
The authors warn that the study is blind to the other, known, detrimental effects of alcohol consumption (such as heart and liver disease) and speculate that the results may be due to an anti-inflamatory effect of alcohol, which - only in those with the right genes - means the cognitive protective effects can outweigh the cognitively harmful ones.
Category(s):Addictions
Source material from The British Psychological Society
