The Monday Effect Revisited: A Diary and Sleep Actigraphy Study

Abstract

Purpose Accidents are more likely to occur during the morning hours of Mondays (Monday effect). This might be due to a higher level of cognitive failure on Monday morning at work.

Methods In a pilot actigraphy study across one working week, we explored this Monday effect and regressed daily self-reported workplace cognitive failure on weekdays (Monday versus other days), background social stressors at work, delayed sleep onset and sleep duration. Diary data were gathered from 40 full-time employees.

Results Confirming our assumptions, results revealed work-related cognitive failure and sleep-onset latency on the previous night to be higher on Mondays compared to other workdays. Work-related cognitive failure correlated positively with delayed sleep-onset latency and background social stressors. In multilevel regression analysis, Monday significantly explained variations in workplace cognitive failure. The addition of background social stressors at work and sleep-onset latency to the regression model showed unique contributions to the prediction of workplace cognitive failure. No significant two-way or three-way interactions between working days, sleep-onset latency or sleep duration, and background social stressors were found.

Conclusion Peak levels of cognitive failure on Monday morning and the association of cognitive failure with social stressors at work contribute to understanding the mechanisms involved in the increased prevalence of occupational accidents on Monday morning. Occupational safety interventions should address both social stressors at work and individual sleep hygiene.