Effect of smoking and time on cognitive function in the elderly without dementia

Objective: To examine the association between smoking and changes in cognitive function over time in elderly persons without dementia. Methods: The results of neuropsychological tests grouped into domains of memory, abstract-visuospatial, and language, from several intervals over a 5-year period in 791 elderly patients without dementia or cognitive impairment. Smoking history was categorized as never, current, or past smokers and related to the slope of performance in each cognitive domain using generalized estimating equations. Results: Performance in all cognitive domains declined over time. Memory performance declined more rapidly among current smokers aged > 75 years than in nonsmokers similar in age, including those who never smoked or had quit smoking. The effect was stronger among those without an APOE-epsilon 4 allele. There was no association between smoking and performance in any cognitive domain in persons aged < 75 years, and there was no association between past smoking and performance on any of the three cognitive factors at any time interval in either age group. Conclusion: Current smokers aged > 75 years perform more poorly on cognitive tests and appear to decline in memory more rapidly than their peers who do not smoke, especially if they lack the APOE-epsilon 4 allele. Smoking does not affect cognitive performance in those persons aged < 75 years.