Study objectives: Only a few studies have examined the possible association between excessive daytime sleepiness (EDS) and risk of occupational injuries, and most of them were based on self-reports. This study tested this association in daytime workers using injury data taken from organizational archives.
Design: A retrospective and prospective study. It covered injury occurrence during two years prior to a sleep disorder assessment/education procedure and injury occurrence in the following year. The workers were given the assessment results and, when applicable, a letter to the treating physician.
Setting: Eight industrial plants. Lectures and discussions on sleep disorders, treatment, and implications to safety and quality of life were conducted with small groups who completed the sleep assessment questionnaire beforehand. The workers completed the sleep assessment questionnaire prior to the lecture/discussion.
Participants: 532 non-shift daytime workers.
Measures and results: A battery of questionnaires to assess EDS (by the Epworth Sleepiness Scale), suspected sleep disorders, sleep habits, and job and environmental conditions. Of the workers studied 22.6% had EDS. Most of those (96.3%) indicated that they had experienced this propensity for the past two years or more and 56% of them had experienced it for 10 years or more. Logistic regression analysis indicated that during the two-year period prior to the procedure, EDS was associated with an increased risk of sustaining a work injury (OR=2.23, 95% CI 1.30-3.81), even after controlling for possible confounders, including factory category, job and environmental conditions. In the year after the procedure, the injury rate decreased by one-third in the workers with EDS but remained unchanged in the workers without EDS. Consequently, the association between EDS and injury was no longer significant (OR=1.42, 95% CI 0.71-2.85).
Conclusion: EDS is a prevalent phenomenon in non-shift daytime workers. Workers with EDS had over two-fold higher risk of sustaining an occupational injury. Providing workers with the assessment results and of the implications of EDS for safety may explain the decrease in occupational injuries upon follow-up. This decrease might have occurred either because of workers taking steps to reduce EDS and/or adopting safety behaviors.