A new study suggests that smoking and heavy drinking speeds up cognitive decline.
Researchers from UCL (University College London) found that smokers who drank alcohol heavily had a 36 percent faster cognitive decline compared to non-smoking moderate drinkers.
Smoking and heavier alcohol consumption often co-occur, and their combined effect on cognition may be larger than the sum of their individual effects.
The research team assessed 6,473 adults (4,635 men and 1,838 women) aged between 45 and 69 years old over a 10-year period. The adults were part of the Whitehall II cohort study of British civil servants.
All the participants were asked about their cigarette and alcohol consumption, and their cognitive function (including verbal and mathematical reasoning, short-term verbal memory and verbal fluency) was then assessed three times over 10 years.
The research team found that in current smokers who were also heavy drinkers, cognitive decline was 36 percent faster than in non-smoking moderate drinkers.
This was equivalent to an age effect of 12 years - an additional two years over the 10-year follow up period.
Among smokers, cognitive decline was found to be faster as the number of alcohol units consumed increased.
The findings are published in the British Journal of Psychiatry.