The findings help explain how smoking is associated with Alzheimer’s disease and dementia.
Smoking shrinks the brain, according to a study by researchers at Washington University School of Medicine in St. Louis. The good news is that quitting smoking prevents further loss of brain tissue, but it still doesn’t mean your brain will return to its original size. Smoking effectively causes premature aging of the brain, the researchers said, as the human brain naturally loses volume as we age.
The survey results are Biological Psychiatry: Global Open Sciencehelps explain why smokers are at higher risk for age-related cognitive decline. Alzheimer’s disease disease.
The neglected effects of smoking on the brain
“Until recently, scientists have overlooked the effects of smoking on the brain, in part because they have focused on all the terrible effects it has on the lungs and heart,” said Laura, senior author of the alumni gift. – said J. Bierut, MD. She is a professor of psychiatry. “But when we started looking at the brain more closely, it became clear that smoking is also very bad for the brain.”
The relationship between smoking, brain size, and genetics
Scientists have long known that smoking and reduced brain volume are linked, but they weren’t sure which was the trigger. And his third factor to consider: genetics. Both brain size and smoking behavior are inherited. Approximately half of a person’s risk of smoking is thought to be due to their genes.
To uncover the relationship between genes, brain, and behavior, Bierut and first author graduate student Yun-Fu Zhang used a publicly available biomedical database containing genetic, health, and behavioral information on 500,000 people. We analyzed data extracted from the UK Biobank. Most are European. Some of the more than 40,000 UK Biobank participants underwent brain imaging tests that can be used to measure brain volume. In total, the team analyzed anonymized data on brain volume, smoking history, and genetic risk for smoking in 32,094 people.
Interaction of genetics, smoking, and brain volume
Each pair of factors was shown to be associated: smoking history and brain volume. Genetic risk of smoking and smoking history. Smoking and genetic risk for brain volume. Additionally, the association between smoking and brain volume is dose-dependent: the more packs a person smokes in a day, the smaller their brain volume.
When all three factors were considered together, the association between genetic risk of smoking and brain volume disappeared, but the association between each factor and smoking behavior remained. The researchers used a statistical approach known as mediation analysis to unravel the chain of events that leads to genetic predisposition to smoking, which in turn leads to reduced brain volume.
Irreversible consequences and prevention
“It sounds bad, and it’s bad,” Biluto said. “Decrease in brain volume is consistent with the progression of aging. This is important as the population ages, as aging and smoking are both risk factors for dementia.”
And unfortunately, this shrinkage doesn’t seem to be reversible. Researchers analyzed data from people who quit smoking years ago and found that their brains remained permanently smaller than those who had never smoked.
“We can’t undo the damage that has already been done, but we can avoid causing further damage,” Chan said. “Smoking is a modifiable risk factor. There’s one thing you can change to prevent brain aging and increased risk of dementia: stop smoking.”
Reference: “Investigating the relationship between smoking behavior and global brain volume” by Yoonhoo Chang, Vera Thornton, Ariya Chaloemtoem, Andrey P. Anokhin, Janine Bijsterbosch, Ryan Bogdan, Dana B. Hancock, Eric Otto Johnson, and Laura J. Bierut. , 6 October 2023 Biological Psychiatry Global Open Science.
DOI: 10.1016/j.bpsgos.2023.09.006