Male smokers lose brain function faster as they age
Men who smoke suffer a more rapid decline in brain function as they age than their non-smoking counterparts, with their cognitive decline as rapid as someone 10 years older but who shuns tobacco, scientists said on Monday.
In a large, long-term study, British researchers found that while there seems to be no link between cognitive decline and smoking in women, in men, the habit is linked to swifter decline, with early dementia-like cognitive difficulties showing up as early as the age of 45.
The research adds to an already large body of evidence about the long-term dangers of smoking - a habit the World Health Organisation refers to as “one of the biggest public health threats the world has ever faced.”
Smoking causes lung cancer, which is often fatal, and other chronic respiratory diseases. It is also a major risk factor for cardiovascular diseases, the world’s number one killers.
“While we were aware that smoking is a risk factor for respiratory disease, cancer, and cardiovascular disease, this study shows it also has a detrimental effect on cognitive ageing and this is evident as early as 45 years,” said Severine Sabia of University College London, who led the study and published it in the Archives of General Psychiatry journal.
A male regular smoker has a higher risk of rapid cognitive decline, compared to his counterparts who do not smoke, researchers from University College London, England, reported in Archives of General Psychiatry. The authors add that the evidence has been mounting regarding the link between smoking and dementia in elderly individuals - smoking has been found to push up the total number of patients with dementia around the world.
Séverine Sabia, Ph.D., and team set out to determine what impact smoking might have on men during their transition from middle age to old age. They gathered data from the Whitehall II cohort study, which was based on people who worked in the British Civil Service. They analyzed data on 2,137 females and 5,099 males whose average age at their first cognitive assessment was 56 years.
They specifically looked at six assessments of individuals’ smoking status over a 25-year-period, as well as three cognitive assessments which took place over a decade.
In an interview she said one explanation for the gender difference found in this study might be the larger amount of tobacco smoked by men, or the fact that there was a significantly lower proportion of women than men among those involved in the research.
Sabia’s team looked for possible links between smoking history and cognitive decline in the transition from midlife to old age using data from 5,099 men and 2,137 women who are involved in a large research project called the Whitehall II study, which is based on employees of the British Civil Service.
The researchers found that:
Males smokers had a higher risk of accelerated cognitive decline
Those men who carried on smoking after follow-up had even greater cognitive decline, according to the test results
Even the regular smokers who had quit during the 10 years before their first cognitive assessment still have a higher-than-average risk of suffering cognitive decline, particularly in executive function. Executive function refers to such cognitive processes as working memory, attention, solving problems, verbal reasoning, mental flexibility, multi-tasking, inhibition, and monitoring of actions.
Long-term ex-smokers had the same risk of cognitive decline as lifetime non-smokers.
The average age of those taking part was 56 when they had their first cognitive assessment.
The study used six assessments of smoking status over 25 years and three cognitive assessments over 10 years, and found that smokers showed a cognitive decline as fast as non-smokers 10 years older than them.
“A 50 year old male smoker shows a similar cognitive decline as a 60 year old male never smoker,” Sabia explained.
Smoking, dementia and cognitive decline
A review of comparable research published to date has concluded that older smokers may have a greater risk of developing dementia (including Alzheimer’s disease and vascular dementia) and cognitive decline than non-smokers. This meta-analysis showed that current smokers had a 40–80% increased likelihood of experiencing dementia and cognitive decline compared with never smokers. The authors of this review observe that individual lifestyle and physiological factors may also influence the association between smoking, dementia and cognitive decline, and that further research is needed.
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Tobacco in Australia
A comprehensive review of the major issues in smoking and health in Australia, compiled by Cancer Council Victoria.
She also found that men who quit smoking in the 10 years before the first cognitive testing point were still at risk of greater cognitive decline, especially in executive function - which covers various complex cognitive processes involved in achieving a particular goal.
Long-term ex-smokers, however, did not show a faster decline in their brain functions or cognitive abilities.
Researchers said there are several factors that could explain the connection between smoking and mental decline. One reason could lie in the way smoking affects the heart, lungs and blood vessels. Because smoking ups the risk of vascular disease, it could limit the body’s ability to deliver the blood, oxygen and nutrients the brain needs to function at its best.
Dr. Charles DeCarli, director of the Alzheimer’s Disease Center at the University of California at Davis, said differences in cardiovascular disease may also explain why the study found that men showed more cognitive decline linked to smoking than women did.
“Men have more heart disease and greater stroke risk than women do up until about age 70 or so. Part of that is related to lifestyle,” DeCarli said. “Men of this age group often smoked more than women did.”
Sabia said more research is now needed to find out why there was a difference between men and women in this study, and to look into possible mechanisms that might link declining brain function to smoking.
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By Kate Kelland
LONDON