The cognitive benefits of smoking cessation were greatest among individuals who gained no more than 5 kg after quitting, whereas greater weight gain was associated with loss of these benefits.
Smoking cessation is associated with a lower risk for dementia and a slower rate of cognitive decline among older adults, though substantial weight gain after quitting appears to diminish these benefits, according to study findings published in Neurology
Smoking is a well-established risk factor for cardiovascular disease and cancer, but its relationship with dementia prevention remains less clear. Because weight gain frequently occurs after smoking cessation and has been linked to adverse metabolic outcomes, researchers investigated whether postcessation weight changes influenced the association between quitting smoking and long-term cognitive health
The researchers conducted a prospective cohort study using data from the US Health and Retirement Study collected between 1995 and 2020. The analysis included 32,802 adults who were free of dementia at baseline. Participants had a mean age of 60.5 years, 57.1% were women, and 73.4% were White. At study entry, 20.4% of participants were current smokers, 36.4% were former smokers, and 43.2% had never smoked
These results suggest that public health interventions aimed at reducing smoking-related dementia risk should consider not only the promotion of smoking cessation but also weight management with quitting to maximize the health benefits
Smoking status and body weight were assessed every 2 years, and incident dementia was identified using the validated Langa-Weir algorithm. Cognitive performance was evaluated over time using a 27-point cognitive assessment scale
During a maximum follow-up of 25 (IQR, 4.4-16.4) years, the researchers documented 5868 participants with dementia. Compared with participants who continued smoking, individuals who quit smoking during follow-up had a significantly lower risk for dementia (hazard ratio [HR], 0.84; 95% CI, 0.73-0.95). Similar reductions were observed among participants who had quit before study enrollment (HR, 0.79; 95% CI, 0.72-0.87) and among those who had never smoked (HR, 0.75; 95% CI, 0.69-0.83)
Analysis of smoking cessation duration showed that dementia risk progressively declined with increasing time since quitting. Risk estimates approached those observed among individuals who had never smoked approximately 7 years after smoking cessation, although the researchers noted that estimates beyond this point were associated with wider confidence intervals and should be interpreted with caution
The researchers further evaluated the effect of weight gain after quitting smoking. The reduction in dementia risk was primarily observed among participants who experienced no weight gain or only modest weight gain after cessation. Compared with current smokers, individuals who quit smoking without gaining weight had an HR for dementia of 0.83 (95% CI, 0.69-0.99), while those who gained 0.1 to 5.0 kg had an HR of 0.73 (95% CI, 0.60-0.90)
In contrast, participants who gained between 5.1 and 10.0 kg after quitting smoking did not experience a statistically significant reduction in dementia risk (HR, 0.87; 95% CI, 0.66-1.15). Similarly, smoking cessation accompanied by weight gain exceeding 10 kg was not associated with a significant reduction in dementia risk (HR, 1.33; 95% CI, 0.97-1.82)
Among 3419 participants who quit smoking and underwent repeated cognitive testing, smoking cessation was associated with a slower rate of cognitive decline compared with continued smoking. The researchers found no evidence of an abrupt improvement in cognition immediately after quitting; however, those who quit smoking experienced a slower decline over time, corresponding to a 15% reduction in age-related cognitive deterioration
The benefit was most pronounced among participants who gained little or no weight after smoking cessation. Those with no weight gain or weight gain of up to 5 kg experienced an approximately 20% slower rate of cognitive decline than those who continued smoking. No significant improvement in cognitive trajectory was observed among participants who gained more than 5 kg
Overall findings were generally consistent across prespecified subgroups, although the association between smoking cessation and lower dementia risk appeared stronger among men and participants who engaged in regular vigorous physical activity. Results also remained generally consistent across multiple sensitivity analyses
Study limitations include reliance on self-reported smoking status and body weight, the observational design, and the possibility of residual confounding. The study authors also noted that smoking behavior between 2-year study assessments may not have been fully captured, potentially resulting in exposure misclassification
“These results suggest that public health interventions aimed at reducing smoking-related dementia risk should consider not only the promotion of smoking cessation but also weight management with quitting to maximize the health benefits,” the study authors concluded
Disclosures: This research was supported by the “Leading Goose” R&D Program of Zhejiang. Please see the original reference for a full list of disclosures
Chen H, Wang J, Lai S, et al.Smoking cessation, weight change, and risk of dementia: a prospective cohort study.Neurology. 2026;106(12):e218123. doi:10.1212/WNL.0000000000218123
