Objectives: We studied the effect of smoking on cognitive decline over a 5-year period at middle age (43 to 70 years).
Methods: In the Doetinchem Cohort Study, 1964 men and women in the Netherlands were examined for cognitive function at baseline and 5 years later. The association between smoking status and memory function, speed of cognitive processes, cognitive flexibility, and global cognitive function were assessed.
Results: At baseline, smokers scored lower than never smokers in global cognitive function, speed, and flexibility. At 5-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. Among ever smokers, the declines in all cognitive domains were larger with increasing number of pack-years smoked.
Conclusions: Interventions to prevent or stop people from smoking may postpone cognitive decline in middle-aged persons.