Quitting smoking even later in life can slow dementia onset, scientists say

Quitting smoking even later in life can slow down cognitive decline and delay the onset of dementia symptoms, according to a new study.

The comprehensive study, published in The Lancet Healthy Longevity, assessed health data of some 9,500 people aged 40 and above across 12 countries and found that those who quit smoking had markedly slower deterioration of verbal fluency and memory six years after quitting.

The findings, researchers at University College London say, underline the importance of quitting smoking as a preventative strategy for dementia.

“Our study suggests 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 quit,” said Mikaela Bloomberg, an author of the study from UCL.

“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.”

Previous studies have shown that quitting smoking is often followed by improvements in physical health and well-being, with hints of short-term improvement in cognitive function after people stop the habit.

Whether this improvement was sustained over the longer term, particularly among those who quit smoking later in life, remained unknown.

To answer this question, researchers at UCL looked at data from three ongoing studies in which a nationally representative group of participants from England, the US and 10 other European countries answered survey questions every two years.

The survey included over 4,700 participants who had quit smoking and an equal number who carried on smoking.

The researchers found that memory and verbal fluency test scores declined at a similar rate for both groups in the six years they all smoked. But these trajectories diverged in the six years following smoking cessation for one of the groups.

The rate of decline was 20 per cent slower for memory and 50 per cent slower for verbal fluency for the group that quit smoking.

This suggested that with each year of ageing, people who quit smoking experienced three to four months less memory decline and six months less fluency decline than those who continued smoking.

Since the study is observational and does not prove cause and effect, the researchers call for further research to validate the findings.

However, they note the findings are consistent with earlier studies showing that adults aged over 65 who quit smoking early or in mid-life return comparable cognitive scores to never-smokers.

“Evidence that quitting may support cognitive health could offer new compelling motivation for this group to try and quit smoking,” Dr Bloomberg said.

“Also, as policymakers wrestle with the challenges of an ageing population, these findings provide another reason to invest in tobacco control,”