Work Hours and Cognitive Function: The Multi-Ethnic Study of Atherosclerosis (MESA)

Abstract Background Cognitive impairment is a public health burden. Our objective was to investigate associations between work hours and cognitive function. Methods MESA participants (n=2,497; 50.7% men; age range 44-84 years) reported hours per week worked in all jobs in exams 1 (2000-2002), 2 (2002-2004), 3 (2004-2005), and 5 (2010-2011). Cognitive function was assessed (Exam 5) using the Cognitive Abilities Screening Instrument (CASI, version 2), a measure of global cognitive functioning; the Digit Symbol Coding (DSC), a measure of processing speed; and the Digit Span test (DS), a measure of attention and working memory. We used a prospective approach and linear regression to assess associations for every 10 hours of work. Results Among all participants, associations of hours worked with cognitive function of any type were not statistically significant. In occupation-stratified analyses (interaction p=0.051), longer work hours were associated with poorer global cognitive function among Sales/Office and blue-collar workers, after adjustment for age, sex, physical activity, BMI, race/ethnicity, educational level, annual income, history of heart attack, diabetes, Apoe4 allele status, birth-place, number of years in the US, language spoken at MESA Exam 1, and work hours at Exam 5 (β=-0.55, 95% CI=-0.99, -0.09) and (β=-0.80, -1.51, -0.09) respectively. In occupation-stratified analyses (interaction p=0.040), we also observed an inverse association with processing speed among blue-collar workers (adjusted β=-0.80, -1.52, -0.07). Sex, race/ethnicity, and Apoe4 did not significantly modify associations between work hours and cognitive function. Conclusions Weak inverse associations were observed between work hours and cognitive function among Sales/Office and blue-collar workers.