Quitting smoking preserves memory and thinking skills, even later in life

A major international study brings good news for longtime smokers: it’s never too late to quit. Researchers found that people who stopped smoking in mid-to-late adulthood had slower declines in memory and verbal fluency than those who kept smoking. The study, published in The Lancet Healthy Longevity, tracked nearly 10,000 adults aged 40 to 89 across 12 countries over 18 years.

Led by Dr. Mikaela Bloomberg at University College London, the research combined data from three large aging studies—the English Longitudinal Study of Ageing, the U.S. Health and Retirement Study, and the Survey of Health, Ageing and Retirement in Europe. Together, they offered a rare global look at how quitting cigarettes can benefit the brain.

“Older adults are less likely to try to quit smoking,” Bloomberg said. “But our findings suggest that stopping even later in life can meaningfully improve long-term brain health.”

Researchers followed 9,436 participants, about half of whom quit smoking during the study. Both groups were similar in age, education, income, and initial cognitive ability. The average participant was 58 years old, and just over half were women.

To measure brain function, the team focused on two key skills—episodic memory and verbal fluency—important indicators of aging. Memory was tested through word recall, while verbal fluency was measured by naming as many animals as possible in a short time. Before quitting, both groups showed similar rates of cognitive decline. But six years later, clear differences appeared: those who quit smoking declined more slowly in both memory and verbal ability.

On average, ex-smokers’ memory declined about 0.05 standard deviations less than continuing smokers—a modest figure that translates to roughly three years’ delay in cognitive aging. Verbal skills declined at a similar rate.

Cigarette smoke fills the body with toxins that cause inflammation, harm blood vessels, and limit oxygen flow to the brain. This stress speeds up brain aging and raises dementia risk. The new findings suggest that quitting can partly reverse these effects.

“Smoking cessation seems to do more than stop further harm—it may actually slow the natural decline that comes with aging,” Bloomberg said.

The team found that the brain benefits were similar regardless of when participants quit. Whether they stopped in their 40s, 50s, or 60s, their cognitive decline slowed in comparable ways.

The improvements might sound small, but their long-term impact is meaningful. Those who quit smoking experienced about 20% slower memory decline and 50% slower loss in verbal fluency than those who continued. That’s roughly three to four months less memory loss and up to six months less verbal decline for each year of aging.

For comparison, most dementia drugs slow decline by less than half a year over 18 months—far less than the gains from quitting smoking.

Around 57 million people worldwide live with dementia, and that number is expected to rise sharply as populations age. Because dementia develops gradually, even small delays in cognitive decline can push back symptoms by years—saving individuals and health systems enormous costs.

“This kind of improvement from a lifestyle change is remarkable,” Bloomberg said. “It shows that quitting smoking—even late in life—benefits not just your heart or lungs, but your brain too.”

Co-author Professor Andrew Steptoe of University College London said the results strengthen the case for including smoking cessation in dementia prevention efforts. “Slower cognitive decline is linked to lower dementia risk,” he said. “These findings support quitting as a potential protective strategy.”

The study harmonized data from 12 countries—including England, Germany, Sweden, France, Italy, Spain, and the U.S.—to ensure fair comparisons. Every two years, participants reported smoking habits and completed standard memory and thinking tests.

Those who quit were also less likely to report lung disease, stroke, or psychiatric issues than those who continued smoking, even though both groups started with similar health profiles.

Because this was an observational study, it can’t prove cause and effect. Still, the clear before-and-after patterns strongly suggest that quitting drives the benefit.

The study’s main strengths were its long follow-up, large sample size, and careful matching between groups. The biggest limitations were that smoking status and health data were self-reported, which can introduce errors. Participants who survived to take part may also have been healthier than average smokers.

Even so, the consistent results across multiple countries give the findings credibility. The work adds to evidence that former smokers eventually share dementia risk levels similar to people who never smoked, especially after about a decade of quitting.

Despite decades of public health campaigns, older adults remain among the least likely to quit smoking—often believing it’s too late to help. This study shows that’s not true.

“Middle-aged and older smokers are less likely to try to quit than younger groups, yet they experience more of the harms,” Bloomberg said. “Knowing that quitting may protect the brain could motivate more people to stop.”

For policymakers, the results provide a new reason to invest in smoking cessation programs for older adults. Even modest cognitive benefits could delay dementia onset for millions.

Quitting smoking at any age can help protect the brain, not just the body. By reducing inflammation, improving blood flow, and slowing brain aging, quitting may delay dementia symptoms by several years.

Public health campaigns, the researchers said, should highlight not only the heart and lung benefits of quitting—but also the cognitive ones.

For individuals, the message is simple: stopping smoking at any age is one of the best things you can do for your mind and your body.

Research findings are available online in the journal Lancet Healthy Longevity.

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