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.
"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 Dr Severine Sabia of University College London, who led the study and published it in the Archives Of General Psychiatry.
She said one explanation for the gender difference might be the larger amount of tobacco smoked by men, or the fact that there was a significantly lower proportion of women among those involved in the research.
Dr 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. 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 non-smoker," Dr Sabia explained.
She also found that men who quit smoking in the 10 years before the first cognitive test were still at risk of greater cognitive decline, especially in executive function - which covers various complex cognitive processes involved in achieving a goal.
However, long-term ex-smokers did not show a faster decline in brain functions.