Study: Smoking permanently shrinks the brain, driving up dementia risk

A study concluded the more a person smokes cigarettes, the faster their brain ages, leading to higher risk of dementia.

Smoking cigarettes has long been linked to health issues involving the mouth, lungs and chest. However, a new study has found another negative effect of the harmful habit — this time, involving a smoker's brain.

Researchers out of Washington University School of Medicine in St. Louis, Missouri, found smoking causes the brain to shrink, and stopping smoking doesn't restore it to its original size. And since brains naturally lose volume as a person ages, smoking effectively speeds up the brain's aging process, possibly explaining why older smokers are at a higher risk of having Alzheimer's disease and dementia.

"It sounds bad, and it is bad," said senior author Dr. Laura J. Bierut, alumni-endowed professor of psychiatry. "A reduction in brain volume is consistent with increased aging. This is important as our population gets older because aging and smoking are both risk factors for dementia."

The findings, published in Biological Psychiatry: Global Open Science, were a result of comparing 32,094 smokers' smoking history, brain imaging, genetic predisposition and other health data points.

Ultimately, researchers found genetic risk leads to smoking, which leads to decreased brain volume. Plus, the more a person smokes each day, or with each additional year of smoking, the smaller their brain volume compared to less frequent smokers or those who don't smoke at all.