0703 Detrimental Effects Of Shift Work On Cognitive Functioning: Preliminary Evidence In Retired Adults

Abstract

Introduction: Night shift workers experience sleep disturbances and circadian misalignment, which has long-term consequences for cognitive functioning. Poor cognitive functioning may be one mechanism linking sleep/circadian disruptions in shift workers with the development of Alzheimer's Disease. Cognitive functioning has not been extensively tested in retired shift workers compared to retired day workers who, in retirement, have similar sleep schedules and circadian rhythm patterns. We hypothesized that retired shift workers would have poorer cognitive functioning compared to retired day workers. Methods: Participants were 26 retired day workers and 17 retired night shift workers aged 60-82. Shift workers were defined as regularly working the majority of hours overlapping the interval of 12:00am and 6:00am for seven years or more. Day work was defined as having no more than 18 months of shift work. A standardized neuropsychological battery was used to assess IQ and current cognitive functioning across executive function, episodic memory, and verbal ability domains; these domains have consistent associations with Alzheimer's Disease. Analysis of covariance was used to test the hypothesis that shift workers have worse neurocognitive function than day workers in these domains, after adjusting for education. Results: There was no difference between groups on IQ (p=.30). Retired shift workers performed worse than retired day workers on an executive function task (DKEFS Trail Making Test; p=.01) a measure of episodic memory (California Verbal Learning Test-II short delay free recall; p=.04), and a measure of verbal ability (DKEFS Verbal Fluency-Category Fluency; p=.05). Eight other tasks were not significantly different (ps>.07). Conclusion: Retired shift workers performed significantly worse than retired day workers on several neuropsychological domains and cognitive processes that are associated with preclinical Alzheimer's Disease. These data are consistent with the hypothesis that shift workers may be at an elevated risk of developing Alzheimer's disease. Because all participants were retired and currently sleeping at night, these preliminary results suggest that shift work has long-term detrimental effects on cognitive functioning.