Smoking shrinks critical part of the brain - leading to memory loss

Long-term smoking causes a thinning of the brain's cortex, which can lead to memory loss, according to a major international study.

The cortex - the outer layer of the brain - naturally thins with old age, but smoking appears to accelerate the thinning, effectively ageing smokers' brains more quickly.

The study - the largest of its kind so far - examined more than 500 patients with an average age of 73 - including current smokers, ex-smokers and non-smokers.

All of the subjects had been examined in 1947 as children, and then more data and scans were taken in the last few years.

“We found that current and ex-smokers had, at age 73, many areas of thinner brain cortex than those that never smoked. Subjects who stopped smoking seem to partially recover their cortical thickness for each year without smoking," says the study's lead author Dr Sherif Karama, assistant professor of psychiatry at McGill University.

Although it was possible to recover some of the thickness, this process took a very long time. Even those who had given up smoking 25 years previously still had a thinner cortex.

Having said that, the researchers note that some of the link between a thinner cortex and smoking might be explained not through the impact of cigarette smoke but because data suggests that people with lower IQs are more likely to have a thinner cortex AND to smoke.

"Smokers need to be informed that cigarettes are associated with accelerated cortical thinning, a biomarker of cognitive ageing," say the authors.

However, the fact that your brain can partially recover should serve as “a strong motivational argument” to encourage people to quit.

People with age-related thinning of the cerebral cortex can try and slow the mental decline by taking exercise, getting enough vitamin D and fatty acids and lowering cholesterol.