Quitting smoking in middle age can reduce dementia risk

Smoking is a strong risk factor for dementia. However, people who quit smoking in middle age may, within a decade, reduce their risk of developing dementia to that of people who never smoked, according to a study published in the September 2025 issue of The Lancet Healthy Longevity.

Researchers used data from three large, international analyses that tracked memory and verbal fluency over about 18 years in a total of 9,436 participants ranging from 40 to 89 years old (average age 58, 52% women). All were smokers at the start. Using mathematical models, the researchers compared the cognitive health of 4,718 participants who quit smoking mid-study with 4,718 otherwise similar study participants who continued to smoke.

In the years while they were all smoking, participants in both groups had very similar rates of cognitive decline. But participants who quit smoking showed significantly slower declines over the next six years in both memory and verbal fluency compared with continuing smokers. The findings suggest that people who stop smoking in middle age can reduce their risk of cognitive decline so much that within 10 years their chances of developing dementia are the same as if they had never smoked, the study authors said.

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