Our brain naturally loses volume as we age, but harmful habits can speed up the process and, in fact, new research has found that smoking shrinks the brain and that, although quitting tobacco prevents further loss. of brain tissue, quitting smoking does not reverse the damage and this organ does not recover its original size.
The study was carried out by researchers at the Washington University School of Medicine in St. Louis (USA) who claim that smoking causes the brain to age prematurely. The findings also help explain why smokers have a high risk of developing age-related cognitive decline and Alzheimer’s disease.
“Until recently, scientists have overlooked the effects of smoking on the brain, in part because we focused on all the terrible effects of smoking on the lungs and heart,” said Dr. Laura J. Bierut, professor of psychiatry alumni and lead author. “But as we started to look at the brain more closely, it became clear that smoking is also very bad for the brain.”
Although it was known that there was a relationship between smoking and reduced brain volume, the triggering cause was unknown. In addition, there is another important factor to take into account: genetics, since both brain size and smoking are hereditary and around half of the risk of a person smoking can be attributed to their genes.
The more cigarettes smoked, the smaller the brain volume.
Bierut and first author Yoonhoo Chang, a graduate student, decided to investigate the relationship between genes, brains and behavior, using data from the UK Biobank, a biomedical database that contains genetic, health and behavioral information on half a million people, the majority of European descent. In total, they analyzed de-identified data on brain volume – obtained through brain imaging –, smoking history and genetic risk of smoking from 32,094 people.
Each pair of factors was shown to be related: smoking history and brain volume; genetic risk of smoking and history of smoking; and genetic risk of smoking and brain volume. Furthermore, the association between smoking and brain volume was dose dependent: the more packs of tobacco a person smoked per day, the smaller their brain volume.
When the authors considered all three factors together, the association between genetic risk for smoking and brain volume disappeared, while the link between each of them and smoking behaviors remained. Employing a statistical approach known as mediation analysis, the researchers determined the sequence of events: genetic predisposition leads to smoking, which leads to a decrease in brain volume.
“It sounds bad and it is bad. “A reduction in brain volume is consistent with increased aging.”
“It sounds bad and it is bad,” Bierut declared. “A reduction in brain volume is consistent with increased aging. “This is important as our population ages, because both aging and smoking are risk factors for dementia.”
The findings have been published in Biological Psychiatry: Global Open Science and also reveal that the shrinkage of brain tissue appears irreversible, because by analyzing data from people who had stopped smoking years earlier, the researchers discovered that their brains remained permanently smaller than those of people who had never smoked.
“You can’t undo the damage that has already been done, but you can avoid causing more damage.” “Smoking is a modifiable risk factor. There is one thing you can change to stop aging your brain and increasing your risk of dementia, and that is to stop smoking,” concludes Chang.
