The effect of bright light on fatigue and sleepiness of shift work nurses

Abstract

Introduction: In this study, we assessed the effect of bright light emitted by light box on fatigue, and sleepiness of nurses.

Methods: Forty four healthy female shift work nurses were allocated into two groups of intervention and control. In the first stage, bright light was emitted to the nurses in the intervention group by the light box, and bright light was not emitted to the control group. In the next stage (one month later), we emitted bright light to the control group in the first stage (cross- over design). Main outcome measures assessed were fatigue and sleepiness. We used Visual Analogue Scale (VAS) of fatigue, and, Karolinska Sleepiness Scale (KSS). Fatigue and sleepiness were assessed every hour, during next 24 hours.

Results: During 24 hours of the assessment of fatigue (VAS), the trend of changes in two groups were in opposite direction and almost all the time of 24 hours, the mean value of two groups were significantly different.  In addition, the effect of intervention on the mean values of KSS during 24 hours was significant and the mean values in two groups were significantly different and the trend of changes in two groups were in opposite direction.

Conclusion: The bright light exposure in nurses resulted in changing the trend of fatigue and sleepiness in opposite directions compared to the controls. The minimum of fatigue occurred at 4 am which was time of maximum fatigue in the controls. Also, minimum sleepiness in the cases who were exposed to the bright light was at 4 am.