During the study, the researchers examined people aged 43 to 70 years for cognitive function twice, at the baseline and five years later.
They observed that the smokers scored lower than their non-smoking counterparts in global cognitive function, speed, and flexibility at the baseline.
At the five-year follow-up, decline among smokers was 1.9 times greater for memory function, 2.4 times greater for cognitive flexibility, and 1.7 times greater for global cognitive function than among never smokers.
"Our results indicate that giving up smoking at any age may prevent further smoking-induced cognitive decline. The results stress the need for stop-smoking interventions in order to postpone cognitive decline among middle-aged persons," the study's authors declared.
The study has been published in the online edition of the journal First Look.