Alternative Formulations of Job Strain and Sleep Disturbances: A Longitudinal Study in the United States.

Background: Sleep disturbances are a major public health concern in the United States, leading to adverse health outcomes. In the working population, job strain has been identified as an important risk factor for sleep disturbances, but evidence from the United States remained limited. This study aimed to examine longitudinal associations between job strain and sleep disturbances in the United States, with a focus on the alternative formulations of job strain.

Methods: A total of 1721 participants were drawn from two waves of the Midlife in the United States (MIDUS) study, with an average 9-year follow-up period. Job strain was measured using Karasek's Job-Demand-Control model and operationalized in six formulations: standard quadrant, simplified quadrant, linear, quotient, logarithm quotient, and quartile based on quotient. Generalized Estimating Equations were used to estimate longitudinal associations of alternative formulations of job strain at baseline with sleep disturbances across follow-up. Corrected Quasi-likelihood Information Criterion (QICu) was used to assess the goodness of fit.

Results: All approaches showed that higher job strain at baseline was significantly associated with an increase in sleep disturbances across follow-up. QICu scores indicated that continuous Demand-Control formulations (linear, quotient, logarithm quotient) had better model performance of 4602.66, 4604.28, and 4601.99, respectively. The logarithm quotient showed the best fit.

Conclusions: Our findings imply the importance of early workplace interventions in reducing job strain to improve sleep hygiene. They further show that the continuous formulations quantifying job strain were more consistent and robust, which provides suggestions for future workplace health research in the United States.