Doctors have proven that smoking causes brain shrinkage
American scientists have found that smoking reduces the size of the brain and leads to premature aging of this organ. Quitting the bad habit can prevent further loss of brain tissue, but still does not return its original size.
Previous studies have suggested that brain volume is related to cigarette smoking. So, this spring, researchers from the University of Pennsylvania (USA) found that smokers on average have smaller brain volume than non-smokers. Each additional pack smoked per year was associated with a decrease in gray matter volume by about 0.15 cubic centimeters.
Until now, however, scientists have debated whether smoking causes a decrease in brain volume or whether smaller brain volume is a risk factor for smoking. In addition, there is a third factor - genetics. It is known that both brain size and the propensity to smoke are inherited. About half of a person's risk of smoking is due to their genes.
Specialists from Washington University School of Medicine in St. Louis (USA) tried to "unravel" the relationship between genes, brain and behavior. They examined this question using several methods of directional assessment: the Bradford Hill criteria, which are usually used to understand causality in epidemiologic studies, and mediation analysis. The results are published in Biological Psychiatry: Global Open Science.
Scientists analyzed data from the British Biobank, a publicly available biomedical database that contains genetic, medical and behavioral information on half a million people, mostly of European descent.
A subset of more than 40,000 British Biobank participants underwent brain imaging to determine their brain volume. In total, scientists analyzed anonymized data on the volume of this organ, smoking history and genetic risk of developing the bad habit in 32,094 people.
Each pair of factors proved to be interrelated: smoking history and brain volume; genetic risk of smoking and smoking history; and genetic risk of smoking and brain volume. In addition, the relationship between smoking and brain volume was dose-dependent: the more cigarettes a person smoked per day, the smaller their brain volume was.
When the three factors were considered together, the association between genetic risk of smoking and brain volume disappeared, while the association between each of these factors and smoking behavior remained.
Using a statistical approach known as mediation analysis, the researchers determined a sequence of events: a genetic predisposition leads to smoking, which triggers a decrease in brain volume.
A few months ago, an international team of scientists found that early smoking in men can lead to their children being born with obesity, asthma and other lung problems.