A recent study conducted by researchers at Washington University School of Medicine in St. Louis has shed light on the detrimental effects of smoking on the brain.
The findings indicate that smoking is likely associated with a reduction in brain size and premature aging of the brain. While quitting smoking can prevent further brain tissue loss, it does not fully restore the brain to its original size, leaving lasting damage.
The research, published in Biological Psychiatry: Global Open Science, offers insight into why smokers are at a heightened risk of age-related cognitive decline and conditions such as Alzheimer’s disease.
Senior author Laura J. Bierut, MD, emphasized that the study’s focus on the brain’s impact was relatively recent, as previous attention had been primarily on smoking’s detrimental effects on the lungs and heart. However, closer examination has revealed that smoking has significant adverse effects on the brain.
The link between smoking and smaller brain volume has been recognized for some time, but it was unclear whether smoking led to reduced brain size or vice versa.
Additionally, genetic factors play a role in both brain size and smoking behavior. Approximately half of a person’s risk of smoking can be attributed to their genetic makeup.
To disentangle this complex relationship between genetics, brain size, and smoking behavior, the researchers analyzed data from the UK Biobank, a comprehensive biomedical database with information on over 500,000 individuals, primarily of European descent.
Brain imaging data from over 40,000 UK Biobank participants were used to assess brain volume. The study involved the analysis of de-identified data on brain volume, smoking history, and genetic risk for smoking for 32,094 individuals.
The results revealed interrelated factors: a history of smoking and brain volume, genetic risk for smoking and smoking history, and genetic risk for smoking and brain volume.
Furthermore, the link between smoking and brain volume was dose-dependent, meaning that the more packs a person smoked per day, the smaller their brain volume.
When considering all three factors together, the association between genetic risk for smoking and brain volume disappeared, while the relationships between each factor and smoking behavior remained.
Through mediation analysis, the researchers determined the sequence of events: genetic predisposition led to smoking, which, in turn, led to a decrease in brain volume.
The study’s implications are concerning, as a reduction in brain volume is associated with accelerated aging. This finding is particularly significant as the global population ages because both aging and smoking are risk factors for dementia.
Moreover, the study found that the brain shrinkage resulting from smoking appears to be irreversible. Even among individuals who had quit smoking years earlier, their brain sizes remained permanently smaller compared to those who had never smoked.
Yoonhoo Chang, the study’s first author, emphasized the importance of quitting smoking as a modifiable risk factor. While the damage already inflicted on the brain may be irreversible, quitting smoking can prevent further harm.
“You can’t undo the damage that has already been done, but you can avoid causing further damage,” Chang emphasized. “Smoking is a modifiable risk factor. There’s one thing you can change to stop aging your brain and putting yourself at increased risk of dementia, and that’s to quit smoking.”
If you care about smoking, please read studies about smoking may increase heart disease risk by 200% and e-cigarette smoke may cause lung cancer and bladder disease.
For more information about brain health, please see recent studies about the cause of weight gain after smoking cessation, and results showing smoking may cause white scars on the brain.
The research findings can be found in Biological Psychiatry Global Open Science.
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