The influence of overtime on cognitive function as measured by neurobehavioral tests in an occupational setting
Proctor, Susan P.
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This two year cohort study involved 248 workers within the automotive industry and explored the effects of two workplace factors, e.g. overtime and assembly-line work, on behavior and cognitive performance as measured by neurobehavioral tests. Review of the occupational epidemiology literature did not reveal any studies of the effects of cumulative fatigue, as a result of long work days due to overtime, on cognitive abilities or job performance. Overtime, defined as number of hours worked greater than 8 hours per day and/or greater than 5 days per week, was calculated from company payroll records. Subjects were categorized as working a machine-paced, assembly line job based on review of their work histories and characterization of their job codes. Cross-sectional analysis of Year 1 data by multiple linear regression demonstrated that overtime worked the week before testing was significantly associated with increased response times on tasks involving simple and complex attention and executive function and an attention-requiring task of basic verbal abilities. The findings from Year 1 support the hypothesis that overtime per week results in cumulative fatigue which affects cognitive performance in the specific functional domains of attention and executive function. Machine-paced work was significantly associated with impaired performance in the areas of attention and executive function, however no significant mood changes were observed. An increased number of errors on a task of complex attention and executive function, poorer performance on a visual memory task involving attention and new learning skills, and reduced percent correct on a computerized task of attention and motor skills and on an attention-requiring task of basic verbal abilities were observed. Machine-paced work did not significantly affect the observed effects of overtime. The results suggest a different response to the strain produced by machine-paced work than that observed with overtime. Machine-paced work was predictive of a faster response time with increased errors, whereas the fatigue effects of overtime resulted in a slower time to complete a task without a decrease in accuracy. Neither overtime nor machine-paced work was associated with performance on any test in Year 2. It was suspected that fewer subjects working increased overtime hours, loss-to-follow-up, and that two of the tests associated with overtime in Year 1 were not repeated in the Year 2 battery, contributed to the difference in the findings between the two years. Further study is recommended to evaluate the proposed hypotheses regarding the effects of overtime and machine-paced work on cognitive function and to investigate the strategic response difference between overtime and machine-paced work.
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