Carlos Solis
An analysis found people who had about a 16% lower risk of dementia than those who kept smoking. Former smokers’ risk was similar to the risk of people who never smoked.
The Key — Don’t Gain Weight
The crucial detail is how body weight changed after quitting. The brain benefits appeared mainly in participants who gained little or no weight — less than five kilograms in the two years after quitting. If a person gained more than 10 kilograms, the statistically significant link between quitting smoking and reduced dementia risk disappeared.
Authors from Zhejiang University School of Medicine analyzed data from more than 32,000 people of retirement age who did not have . The participants’ average age was about 60, and follow-up lasted nearly 25 years. Every two years, participants reported their smoking status and body weight. During that time, researchers recorded nearly 6,000 cases of dementia.
In addition to diagnosis rates, the team tracked changes in cognitive test scores. Participants who quit and gained almost no weight experienced cognitive decline about 20% more slowly than people who continued smoking. The study also found gradual improvements: the longer people stayed smoke-free, the stronger the positive effect on the rate of cognitive aging on some tests.
Why Weight Gain Makes Things Worse
Obesity and type 2 diabetes raise dementia risk. Weight gain after quitting is common — usually less than five kilograms in the first years, but 10 to 20 percent of people who quit gain more than 10 kilograms. If quitting causes significant weight gain, that can raise the risk of diabetes — and because diabetes raises dementia risk, the weight gain can cancel out some of the benefit from stopping smoking.
What This Means for People Who Want to Quit
Quitting offers benefits far beyond dementia risk and brings many other health gains. But the results suggest people who quit may get the most protection for their brain if they also watch their weight and metabolic health.
The authors recommend including information about possible weight gain in counseling for people who quit smoking so they take steps to manage their weight.
This report is based on material from the journal Neurology.
