How smoking is linked to brain shrinkage

It’s well-known that smoking can cause long-term effects on health and increases the risk of cancer, and cardiovascular diseases. Now, a new study reveals that it can also cause premature brain ageing.

The study, led by researchers from Washington University School of Medicine in St. Louis, shows that while a natural reduction in brain volume usually occurs with age, smoking can cause the brain to age prematurely. According to the university’s press release, these findings could also help explain why smokers are at a high risk of age-related cognitive decline and Alzheimer's disease.

"Up until recently, scientists have overlooked the effects of smoking on the brain, in part because we were focused on all the terrible effects of smoking on the lungs and the heart," senior author Laura J. Bieru said in the statement. "But as we've started looking at the brain more closely, it's become apparent that smoking is also really bad for your brain," Bieru added.

This study, published in the journal Biological Psychiatry: Global Open Science, also examined the relationship between genes, brains and smoking behaviour. For this, they analysed data on brain volume, smoking history and genetic smoking risk for 32,094 people from the UK Biobank.

The researchers found that each pair of factors were linked: history of smoking and brain volume; genetic risk for smoking and history of smoking; and genetic risk for smoking and brain volume. They also noted that the more packs a person smoked per day, the smaller their brain volume.

Further analysis also showed that genetic predisposition leads to smoking, which results in decreased brain volume, the statement explains. “A reduction in brain volume is consistent with increased ageing. This is important as our population gets older because ageing and smoking are both risk factors for dementia,” Bieru added in the statement.

Moreover, the study found that the shrinkage was irreversible. Analyzing data on people who had quit smoking years before showed that their brains remained permanently smaller than those of people who had never smoked. The researchers emphasised quitting smoking is an important factor in stopping the ageing of the brain and decreasing the risk of dementia.

Previous studies have also shown that quitting smoking can significantly decrease health risks. For instance, a 2019 study published in the Journal of the American Medical Association (JAMA), showed that when heavy cigarette smokers with at least a 20 pack-year smoking history quit smoking, their risk of cardiovascular disease decreased by 39% within five years.

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