Having assessed nearly 6,500 individuals over a 10-year period, researchers found that smokers who also drank alcohol heavily had a 36% faster cognitive decline compared to non-smoking moderate drinkers. Also, researchers found that among smokers, cognitive decline was faster as the number of alcohol units consumed increased.
Smoking and heavier alcohol consumption often co-occurs and their combined effect on cognition may be larger than the sum of their individual effects, according to lead researcher Dr Gareth Hagger-Johnson.
"When we looked at people who were heavy-drinking smokers, we found that for every 10 years that they aged their brains aged the equivalent of 12 years,” he said.
“From a public health perspective, the increasing burden associated with cognitive aging could be reduced if lifestyle factors can be modified, and we believe that people should not drink alcohol more heavily in the belief that alcohol is a protective factor against cognitive decline.
"Current advice is that smokers should stop or cut down, and people should avoid heavy alcohol drinking. Our study suggests that people should also be advised not to combine these two unhealthy behaviours – particularly from mid-life onwards. Healthy behaviours in midlife may prevent cognitive decline into early old age."