Long-Term Smoking Cessation Slows Cognitive Decline in Middle-Aged and Older Adults

Middle-aged and older adults who quit smoking experience significantly slower rates of cognitive decline than those who continue smoking, according to an 18-year longitudinal analysis of nearly 10,000 participants published in The Lancet Healthy Longevity.¹

In the 6 years following smoking cessation, memory decline slowed by approximately 20% and verbal fluency decline by roughly 50% compared with continuing smokers, translating to 3 to 4 months less memory decline and 6 months less fluency decline with each year of ageing, according to the findings.¹

“This finding is especially important because middle-aged and older smokers are less likely to try to quit than younger groups, yet they disproportionately experience the harms of smoking," lead author Mikaela Bloomberg, PhD, a senior research fellow at the University College of London Institute of Epidemiology & Health Care, said in a statement.² "Evidence that quitting may support cognitive health could offer new compelling motivation for this group to try and quit smoking."²

Bloomberg and colleagues pointed out that previous small-scale trials have demonstrated short-term cognitive improvements within 6–24 months of cessation, but have left uncertain whether these gains persisted over longer periods, particularly among adults who quit in midlife or later life. The team designed this study to answer that question using 2 decades of cognitive data, a tranche sufficient to examine trajectories before and after cessation.¹

Study Methods

The researchers tapped data from 3 large nationally representative cohort studies: the English Longitudinal Study of Ageing (ELSA), the Survey of Health, Ageing and Retirement in Europe (SHARE), and the Health and Retirement Study (HRS). They matched matched 4,718 participants who quit smoking with 4,718 continuing smokers based on demographic, socioeconomic, and cognitive criteria, then examined memory and fluency trajectories using piecewise linear mixed models.¹

The final analytic sample comprised 9,436 individuals (mean baseline age 58.3 years, 52% women) distributed across England, the United States, and 10 European countries. Smokers who quit reported a mean of 12.1 cigarettes daily compared with 13.5 daily in continuing smokers. The 3 cohorts administered identical cognitive tests—immediate and delayed recall for episodic memory and animal naming for verbal fluency—ensuring a harmonized analysis.¹

The matching strategy strengthened causal inference by ensuring comparable baseline cognitive performance between cessation and continuation groups.

Crucially, the 2 groups demonstrated similar memory and fluency decline before cessation: memory declined at −0.03 SDs (95% CI −0.06 to 0.01, P =.16) and fluency at −0.01 SDs (−0.04 to 0.03, P =.76) in the pre-cessation period.¹

Divergence After Cessation

The picture shifted dramatically following smoking cessation. Memory decline in former smokers measured 0.19 SDs compared with 0.24 SDs in continuing smokers, a difference of 0.05 SDs (95% CI 0.00–0.10, P =.036). Verbal fluency declined 0.05 SDs more slowly in former smokers (0.01–0.10, P =.030). Critically, these benefits held regardless of age at cessation, suggesting quitting offered cognitive advantage whether individuals quit at 45 or 75 years old.¹

“We already know that quitting smoking, even later in life, is often followed by improvements in physical health and well-being," Bloomberg said. "It seems that, for our cognitive health too, it is never too late to quit."²

Smoking is thought to damage cognition through multiple pathways. Researchers believe the drug impairs cardiovascular function by damaging blood vessels supplying oxygen to the brain while triggering chronic inflammation and directly damaging brain cells through oxidative stress—the creation of unstable molecules called free radicals.³ Whether cessation reverses these processes or halts further damage remains incompletely understood, though research suggests excess risk of myocardial infarction, stroke, and cardiovascular death may reduce within five years of cessation,⁴ providing a plausible framework for the observed cognitive benefits.

Limitations and Perspective

As an observational analysis, the study cannot establish causation with certainty. Unmeasured differences between smokers who quit and continuing smokers could theoretically explain findings. The researchers acknowledged that the analyzed sample was somewhat healthier than excluded participants, potentially limiting generalizability. Missing race and ethnicity data from SHARE prevented examination of whether cessation benefits varied by demographic group.¹

They also emphasized the study's substantial strengths: 18 years of cognitive data, large representative sample, international scope, matched comparison groups, and piecewise modeling establishing comparable pre-cessation trajectories. Bloomberg et al note that their findings align with previous research showing that adults over age 65 who quit during early or mid-life achieve cognitive scores comparable to never smokers.⁵

Taking Stock

The cognitive benefits of cessation, roughly 3 to 4 additional months of preservation per year, appear modest in absolute terms. Accumulated over years preceding dementia onset, however, such slowing translates to meaningful postponement. Bloomberg's team calculated that smoking cessation delayed cognitive aging by approximately 3 years over 6 years of follow-up, a benefit exceeding current Alzheimer therapies, which delay progression by around five months over 18 months.⁶

"As policymakers wrestle with the challenges of an ageing population, these findings provide another reason to invest in tobacco control," Bloomberg concluded.² For clinicians counseling older smokers, the message is clear: quitting supports long-term cognitive trajectory, making cessation a preventive strategy for dementia across the lifespan.

References

1. Cognitive decline before and after mid-to-late-life smoking cessation: a longitudinal analysis of prospective cohort studies from 12 countries. Lancet Healthy Longev. Published online october 13, 2025. doi:10.1016/ j.lanhl.2025.100753

2. Quitting smoking, even late in life, linked to slower cognitive decline. News release. University College London. October 14, 2025. Accessed October 14, 2025.

3. Hahad O, Daiber A, Michal M, et al. Smoking and Neuropsychiatric Disease-Associations and Underlying Mechanisms. Int J Mol Sci 2021; 22: 7272

4. Gellert C, Schöttker B, Müller H, Holleczek B, Brenner H. Impact of smoking and quitting on cardiovascular outcomes and risk advancement periods among older adults. Eur J Epidemiol. 2013; 28: 649–58.

5. Deal JA, Power MC, Palta P, et al. Relationship of Cigarette Smoking and Time of Quitting with Incident Dementia and Cognitive Decline. J Am Geriatr Soc 2020; 68: 337–45.

6. Knopman DS, Hershey L. Implications of the Approval of Lecanemab for Alzheimer Disease Patient Care: Incremental Step or Paradigm Shift? Neurology 2023; 101: 610–20.