Research from University College London shows that stopping smoking after middle age is associated with a slower rate of age‑related cognitive decline over the long haul.
Published in The Lancet Healthy Longevity, the analysis examined data from 9,436 adults aged 40 or older (average 58) across 12 countries, comparing those who quit smoking with matched smokers who continued the habit.
The findings revealed that participants who had abandoned cigarettes experienced a markedly reduced drop in cognitive scores over the six years following cessation. For verbal fluency, the decline was cut roughly in half, while memory loss slowed by about 20 %.
Because a gentler decline in cognition is linked to a lower risk of dementia, this study adds to evidence that quitting smoking may serve as a preventive measure against the disease. Further investigation is required to confirm these results.
Lead author Dr. Mikaela Bloomberg, UCL Institute of Epidemiology & Health Care, noted, “Our data suggest that quitting smoking can help preserve cognitive health long after the 50s.” She added, “Given that older smokers are less likely to try quitting, demonstrating a lasting cognitive benefit could offer strong motivation.”
Smoking is known to harm brain health partly through cardiovascular damage—causing vascular injury that impairs oxygen delivery to the brain—and through chronic inflammation and oxidative stress that directly damage neurons.
Co‑author Professor Andrew Steptoe commented, “The association between slower cognitive decline and lower dementia risk supports the idea that smoking cessation may help reduce future dementia likelihood, though dedicated dementia studies are needed.”
Earlier studies had shown short‑term cognitive gains after quitting, but the durability of that improvement—especially for those who stop later in life—remained uncertain.
To investigate this, the team pooled data from three longitudinal surveys that regularly assessed a nationally representative sample every two years in England, the United States, and ten other European nations.
Over 4,700 former smokers were matched with an equal number of continuing smokers, balancing initial cognitive scores, age, sex, education, and country of birth.
While the two groups exhibited similar performance trends in the six years before quitting, their trajectories diverged afterward. For former smokers, the yearly rate of memory decline slowed by ~20 % and verbal fluency decline by ~50 %. Practically, this meant that each year of aging produced three to four months less memory loss and six months less fluency loss, compared with those who kept smoking.
As an observational study, the results cannot conclusively prove causation, but they align with previous reports that adults over 65 who quit earlier in life show cognitive levels comparable to never smokers and a similar long‑term risk of dementia.