WEDNESDAY, June 11 (HealthDay News) -- Middle-aged smokers are at greater risk of poor memory, but studying the impact of smoking on cognition is hampered by the greater rate of loss to follow-up by death and non-participation in tests compared to non-smokers, according to study findings published in the June 9 issue of the Archives of Internal Medicine.
Severine Sabia, of INSERM in Villejuif, France, and colleagues conducted a study of 10,308 subjects aged 35 to 55 at baseline in 1985-1988. The subjects' smoking history was ascertained at baseline and again in 1997-1999, at which point 5,388 subjects also provided cognitive data (on memory, reasoning, vocabulary and semantic and phonemic fluency). Of these, 4,659 were re-tested five years later.
Compared with never-smokers, those who smoked were more likely to be in the lowest quintile for cognitive performance, the investigators found. Those who were ex-smokers at baseline were at 30 percent lower risk of poor vocabulary and low verbal fluency versus smokers. The odds of loss to follow-up by death were also higher for smokers than non-smokers, the researchers report.
"These results may have been underestimated because of premature death and lower participation in cognitive tests among smokers. Stopping smoking in middle age was associated with improvement in other health behaviors and with little residual adverse effect of smoking on cognition," the authors write.
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