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.
Research has also found that, compared to light smokers, the risk of Alzheimer’s disease was significantly higher among medium to heavy smokers. This suggests a possible dose-response relationship between how much someone smokes and their chances of developing Alzheimer’s i.e. the more you smoke, the higher your risk.
Currently we don’t fully understand the reasons why smoking increases the risk of dementia.
But we do know that inhaling tobacco smoke has been linked to oxidative stress. Oxidative stress is an imbalance between toxic molecules inside our cells and the antioxidants we need to remove them. This imbalance causes damage to cells in our body. Research has found that oxidative stress itself is connected to the onset of dementia.
Smoking also increases the risk of developing other risk factors for Alzheimer’s disease and vascular dementia such as stroke and high blood pressure, in addition to being a risk factor in itself. Smoking damages the structure of your blood vessels, making it harder for blood to flow freely around the body and into the brain. It also reduces the oxygen level in your blood.
The brain uses around 20% of the body’s oxygen supply from blood, which means anything stopping the brain from getting an oxygen-rich blood supply is stopping brain cells from getting the nutrients they need to survive, thrive and resist damage.
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.
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.
