Quitting smoking in midlife can protect brain health

Quitting smoking, even later in life, can slow cognitive decline, new research shows.

Researchers at University College London (UCL) examined data from nearly 10,000 people in 12 different countries and found that people who quit smoking in middle age or later showed slower age-related decline in memory and verbal fluency compared with those who continued smoking.

The research team found for verbal fluency, the rate of decline roughly halved, while for memory, it slowed by 20 per cent in those who had quit smoking in the six years since they stopped.

The findings are published in The Lancet Healthy Longevity and suggest that quitting smoking could reduce the risk of developing dementia.

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Smoking and brain ageing

Smoking can accelerate brain ageing by damaging the blood vessels that deliver oxygen and nutrients to the brain. In addition, smoking can trigger chronic inflammation and oxidative stress in the body which can damage parts of the brain. Collectively, these processes can lead to an increased rate of cognitive decline.

Using data from three nationally representative cohort studies in countries, including England, the US, and 10 other European countries, the researchers examined 18 years of cognitive data collected between 2002 and 2020 to determine how cessation of smoking affected the rate of cognitive decline.

The researchers identified people who quit smoking during the study period and matched them to control participants with similar demographic and socioeconomic status, who continued smoking.

The study included 9,436 adults aged between 40 and 89, half of whom quit smoking during the study and half of whom continued smoking. Memory and verbal fluency skills were tracked over time.

In the six years before quitting, matched smokers showed almost identical rates of cognitive decline. However, in the six years after quitting, people who stopped smoking experienced a slower decline in both memory and verbal fluency compared with those who kept smoking.

The rate of decline was about 20 per cent slower for memory and 50 per cent slower for verbal fluency in the people who quit, compared to those who did not. The researchers state that the differences were small but statistically significant and highlight a cognitive benefit to cessation of smoking.

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In practical terms, people who quit experienced three to four months less memory decline and six months less fluency decline than those who continued smoking over each year of ageing.

Benefits of quitting

The benefits of quitting were seen across all age groups, whether this occurred in midlife or later in life.

Lead author Dr Mikaela Bloomberg from the UCL Institute of Epidemiology and Health Care said: ‘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 quit. We already know that quitting 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.’

The researchers say that this finding is significant because middle-aged and older smokers are less likely to try to quit than younger groups. However, they are disproportionately affected by the harms of smoking.

Dr Bloomberg added: ‘Evidence that quitting may support cognitive health could offer new compelling motivation for this group to try and quit smoking. As policymakers wrestle with the challenges of an ageing population, these findings provide another reason to invest in tobacco control.’

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Since slower cognitive decline lowers dementia risk, the researchers suggest that the findings strengthen evidence suggesting that quitting smoking can help prevent the disease, but caution that further research is needed to confirm a causal link between the long-term impact of quitting smoking and dementia risk.