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This study assessed whether self-rated physical and mental work demands were associated with cognition among older working adults and whether their effects were dependent. The cross-sectional sample consisted of 6,377 working older adults using the Health and Retirement Study in 2004. Self-rated work demands were summarized from four questions about the 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. Multivariable linear regression assessed the associations and additive interaction between physical and mental work demands and cognition, adjusted for age, sex, race, education, and practice effect. Independently, higher physical work demands were associated with poorer cognition (change per one unit increase: 0.50, 95% CI: 0.36, 0.65), and higher mental work demands were associated with better cognition (change per one unit increase: -0.31, 95% CI: -0.44, -0.19). The effect of one work demand measure became more negative as the level of the other increased (Beta for interaction = -0.23, 95% CI: -0.43, -0.03). A one-point increase in mental work demands was associated with 0.79 (95% CI: 0.51, 1.08) points higher cognition score when physical work demands were lowest, but was not associated with cognition when physical work demands were highest (0.11, 95% CI: -0.26, 0.48). 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. The associations of self-rated mental and physical work demands on cognition are dependent. Future studies should strongly consider examining interactions to capture the range of work demand effects.
Hickman et al. (Wed,) studied this question.