The more cigarettes smoked, the smaller the brain size, a shocking study reveals
A recent study revealed a surprise when it accused smoking as a possible cause for Alzheimer’s disease, a puzzle that has long baffled scientists.
The research team from the School of Medicine at Washington University in St. Louis suggested that smoking may lead to the shrinkage of brain size and cause premature brain aging.
In the study published in the journal Biological Psychiatry: Global Open Science, researchers aim to explain why smokers are at a greater risk of age-related cognitive decline and Alzheimer’s disease.
The study results concluded that quitting smoking could prevent further brain tissue loss, but it does not restore the brain to its original size.
Laura Beirut, PhD in Medicine and Professor of Psychiatry, said, ‘Until recently, scientists ignored the effects of smoking on the brain, partly because we focused on all the terrible effects of smoking on the lungs and the heart.’
Scientists have known for a long time that smoking and smaller brain size are linked, but they never confirmed the cause, especially in the presence of a third factor to be considered, which is genetics.
In the study, Beirut and the first author of the study, Yunho Chang, a graduate student, analyzed data derived from the UK Biobank, a publicly available vital medical database containing genetic, health, and behavioral information about half a million people, mostly of European descent.
A subset of over 40,000 participants in the UK Biobank underwent brain imaging, which can be used to determine brain size.
Overall, the team analyzed data on brain size, smoking history, and genetic risks of smoking in 32,094 individuals.
It was found that each pair of factors is linked to each other: smoking history and brain size, genetic risks of smoking and smoking history, and genetic risks of smoking and brain size.
Moreover, the association between smoking and brain size depends on the dose, meaning that the more cigarette packs a person smokes daily, the smaller their brain size.
When all factors were taken into account together, the link between genetic risk of smoking and brain size disappeared, while the link between each of these factors and smoking behaviors remained.
Using a statistical approach known as mediation analysis, researchers found that genetic predisposition leads to smoking, which in turn leads to a decrease in brain size.
