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Thursday, 16 October, 2025
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Quitting smoking stubs out dementia risk – London study

British researchers have found that giving up smoking in middle age not only halves the rate of decline in verbal fluency and slows memory loss by 20% but can reduce a person’s cognitive decline so dramatically that within 10 years their chances of developing dementia are the same as someone who has never smoked.

The findings from the study of 9 436 people in England, the US and 10 other European countries add to a growing body of evidence that kicking the habit can slow the rate of mental deterioration from ageing and thus help prevent the onset of dementia, The Guardian reports.

“Our study suggests that quitting smoking may help people to maintain better cognitive health over the long term, even when we are in our 50s or older when we give it up”, said Dr Mikaela Bloomberg of University College London, the lead researcher.

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

Bloomberg and her colleagues from UCL reached their conclusions by comparing the cognitive functioning of adults aged at least 40, who quit, with those who kept smoking. While their performance was the same at the start, the quitters had gained substantial advantages over the smokers when their cognitive capacities were assessed over the next six years.

“Individuals who quit smoking had more favourable (cognitive) trajectories after smoking cessation than continuing smokers,” they write in The Lancet Healthy Longevity.

“The results suggest the importance of smoking cessation, even in later life, for long-term cognitive health.”

Although the findings do not prove cause and effect, they could provide “compelling motivation” for older smokers – who are less likely than younger age groups to try to give up – to do so, the authors added.

Smoking is one of the 14 risk factors for dementia identified by a commission of experts assembled by The Lancet last year. There is growing evidence that tackling these factors, which include depression, drinking too much, hearing loss and high cholesterol, reduce the risk of developing dementia in the first place, they added.

“The findings strengthen existing evidence that changing to a healthier lifestyle can have a measurable impact on your brain health,” said Dr Richard Oakley, the associate director of research and innovation at Alzheimer’s Society.

“We know that quitting smoking, keeping physically active, eating a healthy balanced diet and drinking less alcohol can all help reduce the risk of dementia.”

The paper explains that smoking is thought to contribute to neurodegeneration by harming cardiovascular health, by affecting blood vessels that supply oxygen to the brain, and also by causing chronic inflammation and directly damaging brain cells through oxidative stress.

However, Dr Julia Dudley, head of research at Alzheimer’s Research UK, cautioned that “the greater cognitive decline seen in smokers doesn’t mean that these people will go on to develop dementia”.

Differences between the two groups in their socioeconomic background or alcohol intake may have influenced the results, she said.

Caroline Cerny, deputy chief executive at Action on Smoking and Health (ASH), said: “We’ve known for some time that smoking increases the risk of dementia and cognitive decline, but this important evidence shows that the harms can be slowed by quitting.

“It illustrates just why it is so important to stop smoking at any age, but particularly in middle age before many of the symptoms of cognitive decline will have emerged, and highlights the need for sustained investment in stop smoking services.”

Last month, 35% of smokers in England tried to quit and 29% of them succeeded, almost double the rate seen when records began in 2007.

Study details

Cognitive decline before and after mid-to-late-life smoking cessation: a longitudinal analysis of prospective cohort studies from 12 countries

Mikaela Bloomberg, Jamie Brown, Giorgio Di Gessa, Feifei Bu, Andrew Steptoe.

Published in The Lancet Healthy Longevity on 13 October 2025

Summary

Background
Whether short-term improvements in cognitive performance observed following smoking cessation are transient or if longer-term cognitive trajectories are also improved is unclear, particularly when adults are middle-aged or older at smoking cessation. We examined whether long-term cognitive trajectories improved following mid-to-late-life smoking cessation.

Methods
In this longitudinal study, we used data from three nationally representative cohort studies from 12 countries including 18 years of cognitive data (2002–20). Participants who quit smoking during follow-up were matched with an equal number of continuing smokers according to key demographic, socioeconomic, and cognitive criteria. We used piecewise linear mixed models to examine memory and fluency decline before and after smoking cessation and during a comparable time period in continuing smokers.

Findings
We included data from 9436 participants who smoked (4718 [50·0%] smokers who quit matched with 4718 [50·0%] continuing smokers, aged 40–89 years, with 4886 [51·8%] women and 4550 [48·2%] men). In the six years before smoking cessation, matched smokers who quit and continuing smokers had similar rates of memory and fluency decline (difference in memory decline [smokers who quit–continuing smokers] –0·03 SDs [95% CI –0·06 to 0·01], p=0·16; difference in fluency decline –0·01 [–0·04 to 0·03], p=0·76). In the six years following smoking cessation, smokers who quit had memory and fluency scores that declined more slowly than continuing smokers (difference in memory decline 0·05 SDs [0·00–0·10], p=0·036; difference in fluency decline 0·05 SDs [0·01–0·10], p=0·030). Coefficients for interaction with age at smoking cessation suggested results did not differ by age at smoking cessation (p>0·05 for all).

Interpretation
In middle-aged and older smokers with initially similar cognitive trajectories, smokers who quit subsequently had more favourable trajectories than continuing smokers regardless of age at cessation. As older adults are less likely than younger people to attempt smoking cessation, improvements in long-term cognitive trajectories might provide an additional motivation to quit.

 

The Lancet Healthy Longevity article – Cognitive decline before and after mid-to-late-life smoking cessation: a longitudinal analysis of prospective cohort studies from 12 countries (Open access)

 

The Guardian article – Dementia risk for people who quit smoking in middle age ‘same as someone who never smoked’ (Open access)

 

See more from MedicalBrief archives:

 

Lancet adds to dementia risk factors list

 

Study confirms health lifestyle role in reducing dementia

 

Global study of 70,000 people links dementia to smoking, cardiovascular disease

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