Associations of self‐rated mental and physical work demands with cognition are dependent in a cross‐sectional sample of the Health and Retirement Study

Background The number of older adults remaining in the workforce is growing, but little is known about how physical and mental work demands jointly affect cognitive health. This study assessed whether self‐rated physical and mental work demands were associated with cognition among older working adults and whether their associations were dependent. Methods Our cross‐sectional sample consisted of 6,376 working older adults in the 2004 wave of the Health and Retirement Study. Self‐rated work demands were summarized from four questions about frequency of mental or physical demands in the respondent’s current job. Cognition was assessed using a subset of the Telephone Interview for Cognitive Status. We used multivariable linear regression to test for associations and additive interaction between physical and mental work demands and cognition, adjusted for age, sex, race, education, and practice effect. Result Independently, higher physical work demands were associated (P<0.001) with poorer cognition and higher mental work demands were associated (P<0.001) with better cognition. In an interaction analysis, the effect of one work demand measure became more negative as level of the other increased (B for interaction = ‐0.22, 95% CI: ‐0.42, ‐0.02). A one‐point increase in mental work demands was associated with 0.69 (95% CI: 0.40, 0.99) points higher cognition score when physical work demands were lowest. At the highest level of physical work demands, mental work demands were not associated with cognition (0.11, 95% CI: ‐0.28, 0.49). A one‐point increase in physical work demands was not associated with cognition (0.09, 95% CI: ‐0.30, 0.48) when mental work demands were lowest. At the highest level of mental work demands, physical work demands were associated with ‐0.53 (95% CI: ‐0.78, ‐0.29) points lower cognition score. The highest predicted cognition score was for the highest mental and lowest physical work demands. Results were robust to additional adjustment for health and behavior covariates. Conclusion The associations of self‐rated mental and physical work demand with cognition were dependent. Beneficial cognitive effects of mental work demands may not apply to workers with physically demanding jobs. Future studies should strongly consider examining interactions to capture the range of work demand effects.