Musculoskeletal symptoms in upper extremities and work performance: Cut-off scores and interaction between biomechanical demand and psychosocial job factors

Abstract

Objective: The overall goal of these three dissertation studies was to fill the gap in the literature about the effect of biomechanical and psychosocial job factors on musculoskeletal symptoms in the upper extremities (MSUE) and work performance. Study 1 identified the level of musculoskeletal pain (MSP) in the upper extremities indicating lowered work performance. Study 2 examined whether coworker support, job security, and job satisfaction moderate the paths from biomechanical demand and psychosocial job strain to work performance when mediated by MSUE. Study 3 investigated the interaction between biomechanical demand and psychosocial job strain on MSUE and work performanceMethods: Secondary analysis was carried out using data from a prospective cohort study of full-time workers from nine manufacturing and three healthcare worksites in the state of Washington. Data involved 1) on-site visit individual biomechanical factor assessment; 2) health interview (health history, job history, MSUE status) by trained interviewers; and 3) self-administered psychosocial questionnaire. The level of work performance was measured by Disabilities of the Arm, Shoulder and Hand (DASH) work module. Study 1 adopted receiver operating characteristic (ROC) curve analysis to provide the cutoff for a composite MSP index to detect lowered work performance using baseline data. Study 2 utilized two-group structural equation modeling to examine the moderation effect for each path using baseline data. Study 3 applied multilevel linear regression for MSUE and work performance using data for up to two years. Results: Study 1 showed that MSP index score of 2 (moderate or multisite) achieved the best balance between sensitivity (.79) and specificity (.69) to detect low work performance. Study 2 showed job security moderated the relationship between biomechanical job demand and MSUE (∆x^2(1) =5.03, p=.02), with the low job security group experiencing a stronger effect on MSUE (β=.01, 95% CI: .002, .022) than the high job security group (β=-.01, 95% CI: -.020, .004). Job satisfaction moderated the relationship between MSUE and limited work performance (∆x^2(1) =7.02, p=.01), with the high job satisfaction group (β=8.83, 95% CI: 5.27,12.40) experiencing a weaker effect on limited work performance compared to the low job satisfaction group (β=17.93, 95% CI: 11.86, 24.00). There was no significant moderation effect of coworker support on the three paths. Study 3 indicated workers in the action group (moderate biomechanical exposure) were less likely to have MSUE and limited work performance than workers in the safe group (low biomechanical exposure). Sensitivity analysis showed the buffering effect of job control was smaller in the action group than in the safe group. Conclusions: For study 1, workers need to be encouraged to seek help when their MSP is moderate or experienced in more than one upper extremity body part. For study 2, the impact of biomechanical job demand on MSUE differ by the level of job security and job satisfaction modifies the impact of MSUE on work performance. For study 3, job control may play a greater role in MSUE experience and work performance among workers exposed to low biomechanical exposures, but less among workers exposed to high biomechanical exposures.