0007 A Pilot Study Examining the Relationship Between Work Productivity and Circadian Misalignment in Night Shift Work

Abstract Introduction There has been general agreement that circadian misalignment is a primary driver of poor outcomes associated with night shifts, such as insomnia, excessive sleepiness, and impaired work productivity. However, few studies have utilized gold-standard measures of circadian rhythms (eg, dim light melatonin onset and offset; DLMO and DLMOff) in examining its association with outcomes. This pilot data aimed to examine the magnitude of the relationship between circadian misalignment and work productivity in night shift workers. Methods Participants were fixed night shift workers, engaging in at least three shifts per week with their shift beginning between 18:00 and 02:00 and lasting 8 to 12 hours. DLMO and DLMOff were assessed in-lab with 24 hourly salvia collections. Work productivity was measured with the Endicott Work Productivity Scale (EWPS). Circadian misalignment was operationalized as any overlap of DLMO and DLMOff during the participant's work shift. Insomnia and excessive sleepiness were operationalized as a score of 10 or greater on the Insomnia Severity Index (ISI; referenced to daytime sleep) and the Epworth Sleepiness Scale (ESS). Results Night shift workers with circadian misalignment reported an EWPS score of 43.2 (SD=12.1), while those without circadian misalignment scored 39.6 (SD=15.6). The Cohen’s d effect size was 0.26. In contrast, those with insomnia reported an average EWPS score of 43.9 (SD=13.6) compared to 36.1 (SD=8.5) for those without insomnia (Cohen’s d = 0.69). Furthermore, those with excessive sleepiness had an average EWPS score of 44.7 (SD=14.2), versus 39.1 (SD=10.7) for those without excessive sleepiness (Cohen’s d = 0.44). Conclusion These results suggest that the association between circadian misalignment and work productivity in night shift workers may be smaller than anticipated. Instead, work productivity in night shift worker may be more strongly associated with symptoms of shift work disorder. These data are consistent with evidence that insomnia in non-shift workers are associated with higher absenteeism and presenteeism. This is also consistent with our prior research indicating that symptoms of shift work disorder can be influenced by various factors, including sleep reactivity. Support (if any) Support for this study was provided from the National Heart Lung and Blood Institute R01HL160870 awarded to Dr. Philip Cheng.