Smoking has long been known to harm nearly every part of the body. It damages the lungs, increases the risk of heart disease and stroke, raises the likelihood of several cancers, and shortens life expectancy.
Scientists have also discovered that smoking affects the brain, increasing the risk of memory problems and dementia as people grow older.
Dementia is not a single disease but a group of conditions that affect memory, thinking, reasoning, and daily functioning. Alzheimer’s disease is the most common form of dementia, but there are many others.
As populations age around the world, dementia has become one of the biggest public health challenges, affecting millions of families and placing enormous pressure on healthcare systems.
For years, researchers have encouraged smokers to quit because of the many health benefits. However, some people worry about weight gain after quitting.
It is common for former smokers to gain weight because nicotine suppresses appetite and affects metabolism. This has led some people to wonder whether weight gain after quitting could reduce the health benefits of smoking cessation.
A large new study has provided encouraging answers. Researchers led by Dr. Hui Chen from the First Affiliated Hospital of Zhejiang University School of Medicine examined whether quitting smoking and subsequent weight gain affect the long-term risk of dementia. Their findings were published in the journal Neurology.
The study used data from the U.S. Health and Retirement Study, one of the largest long-term studies of aging adults. Researchers followed 32,802 adults who did not have dementia when the study began. Participants were tracked from 1995 through 2020, allowing scientists to observe health changes over a period of up to 25 years.
During the study, 5,868 participants developed dementia. This large number of cases allowed researchers to carefully compare the experiences of current smokers, former smokers, and people who had never smoked.
The results showed a clear pattern. People who quit smoking during the study had a significantly lower risk of developing dementia than people who continued smoking.
In fact, after quitting, their dementia risk became similar to that of people who had stopped smoking before the study began and also approached the risk seen in people who had never smoked.
The findings became even more interesting when researchers examined weight changes after quitting. The benefits of smoking cessation remained strong among people who gained little or moderate amounts of weight.
Specifically, people who gained five kilograms or less during the first two years after quitting continued to show a clear reduction in dementia risk.
However, for people who gained more than 10 kilograms after quitting, the protective effect appeared weaker. Although the results in this group did not reach statistical significance, the findings suggest that very large weight gain may reduce some of the brain health benefits associated with smoking cessation.
The researchers also discovered that the longer people remained smoke-free, the greater the reduction in dementia risk. The risk continued to fall over time and became increasingly similar to that of people who had never smoked. The greatest improvements appeared to level off about seven years after quitting.
The study also examined cognitive function over time. Researchers found that people who quit smoking experienced a slower decline in memory and thinking abilities over the long term. This slower decline was especially noticeable among those who gained only a small amount of weight after quitting.
These findings provide important reassurance for smokers who are considering quitting. Some people hesitate to stop smoking because they fear gaining a few kilograms. However, the study suggests that modest weight gain does not erase the brain health benefits of quitting.
When reviewing the study, one of its greatest strengths is its large size and exceptionally long follow-up period. Following more than 32,000 adults for up to 25 years provides strong evidence that smoking cessation has lasting benefits for brain health.
The findings also highlight the importance of maintaining a healthy weight after quitting. However, because this was an observational study, it cannot prove cause and effect with complete certainty.
Even so, the evidence strongly suggests that quitting smoking is one of the best decisions a person can make for protecting long-term cognitive health. The message is encouraging: quitting smoking may lower dementia risk, and maintaining a healthy lifestyle afterward may help maximize those benefits.
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Source: Zhejiang University School of Medicine.
