Quitting smoking will stall cognitive decline, no matter how old you are: study

A new study published this week in the Lancet Journal of Health Longevity is reinforcing the negative effects of smoking on cognitive health and offering new evidence to support quitting among seniors.

The research was conducted by scientists at Britain’s University College London, and funded by the (U.K.) National Institute on Aging, National Institute for Health and Care Research. It drew on data from studies conducted in 12 countries, including 18 years (2002–20) of cognitive data.

It involved participants who quit smoking and who were matched with an equal number of continuing smokers according to key demographic, socioeconomic, and cognitive criteria. In all there were 9,436 participants: 4,718 smokers who quit and an equal number of continuing smokers, aged 40–89 years, with 51.8 per cent women and 48.2 per cent men.

The primary conclusion was that in the six years after quitting smoking, which could occur in mid or later life, smokers who quit had memory and cognitive fluency scores that declined more slowly than smokers who did not quit.

The findings of previous small-scale smoking cessation trials have suggested cognitive benefits in the six to 24 months following smoking cessation.

In this study, the researchers did not see improvement in cognitive performance, but instead a reduction in the rate of decline. Their results show later-life quitting is associated with a delay in cognitive decline of up to three years of ageing. And the benefit “accumulates further over time,” they wrote.

The researchers suggest the difference between seeing cognitive benefits in the earlier studies and seeing slower decline in the present one is probably attributable to the younger age distribution in previous studies (with a mean age of 45 years), as well as the fact that memory and fluency generally decline from age 60–65 years onwards.

“The fact that we observed more rapid cognitive decline … when cognitive trajectories were centred (on) age 65, regardless of smoking cessation, is consistent with memory and fluency ageing trajectories.”

“However,” they wrote, “the present findings show adults aged at least 65 years who quit smoking aged 44 years or younger had better cognitive scores than current smokers.”

One of the driving factors of the study is the prevalence of Alzheimer’s disease and related dementias as the eighth leading cause of death in the world, with an estimated 56.9 million people living with dementia globally.

As a result, the researchers wanted to target modifiable risk factors for cognitive decline from midlife onwards.

Among the risk factors, say the researchers, smoking has emerged as a potential cause of accelerated cognitive decline.

“In middle-aged and older smokers with initially similar cognitive trajectories, smokers who quit subsequently had more favourable trajectories than continuing smokers,” they wrote. This was true “regardless of age at cessation.”

One key to conducting the research is that older adults are less likely than younger people to try to quit smoking. The team reasoned that proving improvement in long-term cognitive trajectories might provide additional motivation for older smokers to quit.

“With less than 10% of serious attempts to quit smoking succeeding after 1 year, identifying novel and compelling reasons to attempt to quit remains an important focus for public health initiatives,” they wrote. “These findings suggest the potential reversibility of smoking-related cognitive harms and could motivate older adults to try to quit smoking, offering new evidence to support the public health message that it is never too late to quit.”

The present findings reiterate the negative effects of smoking on cognitive health, the researchers conclude, and “offer new evidence to support smoking cessation at any age.”

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