Brief Morning Exposure to Bright Light Improves Subjective Symptoms and Performance in Nurses with Rapidly Rotating Shifts

Abstract

Methods:We conducted a randomized crossover study involving registered nurses at a teaching hospital working a two-shift system including the night shift. Participants were instructed to expose themselves to BL for 10 min on workday mornings. Results: A total of 61 participants were enrolled in the present study. Thirty-one participants received BL exposure in the first month, and the other 30 received it in the second month. Significant improvements were noted in the BL periods compared with the non-BL periods for self-assessed sleepiness at 10:00 on day-shift days evaluated using the Karolinska Sleepiness Scale, self-assessment of night sleep for day-shift days using the Visual Analogue Scale and for fatigue assessed using the Checklist Individual Strength Questionnaire. The estimated mean difference for each scale (95% confidence interval) was -0.55 (-0.91, -0.20), 0.37 (0.04, 0.70) and -2.13 (-3.78, -0.48), respectively. Mean response time evaluated using the psychomotor vigilance task test (PVT) showed significant improvement in the BL periods compared with the non-BL periods. No statistically significant differences were observed for sleepiness at 14:00, depression, number of PVT lapses or frequency of perceived adverse events and near misses. Conclusion: Our findings suggest that brief BL exposure on mornings preceding a day shift is effective in improving sleepiness and performance during day-shift work, subjective nighttime sleep on day-shift days, and perceived fatigue for the preceding two weeks in rapidly rotating shift nurses. (J Occup Health 2011; 53: 258-266)

Health-related interventions among night shift workers: a critical review of the literature

“…However, of the included interventions that reported on sleepiness, findings were aligned with sleep quality and quantity results (23,24,33,36,42,53,60,64). One exception was a study of Modafinil, which significantly reduced sleepiness during the commute home from a night shift but had no effects on sleep (63).…”

“…Some adverse effects were reported, including insomnia and headache from Modafinil (63,65), and nausea, anxiety, low-back pain, and other effects from Armodafinil (64). Adverse events were also reported across other intervention types such as headaches or feelings of heat/cold in response to bright light exposure (29,30), and difficulty scheduling social or family activities as a result of a shift schedule change (39,41), Several studies stated that no significant adverse events resulted from the interventions (35,36,46,61,62), but most did not report adverse events at all. Since participants were not monitored for adverse health effects beyond the study period in all articles, we could not evaluate potential long-term negative health consequences of the interventions.…”

“…Sample size is another area for improvement. In this review, only three studies reported sample sizes with adequate power to detect a statistically significant difference in primary outcomes of interest (36,58,59,63).…”

“…We excluded self-reported sleepiness as an outcome, as it is more closely related to workplace safety than chronic disease risk (36,43). However, of the included interventions that reported on sleepiness, findings were aligned with sleep quality and quantity results (23,24,33,36,42,53,60,64).…”

“…There was also some indication that phase shift, an indicator of circadian adaptation to night shift work, had occurred, as evidenced by significant body temperature and melatonin changes. Nurses who exposed themselves to bright light for ten minutes on workday mornings reported significant improvements in quality of night sleep on day shifts compared to non-bright light exposure periods (36). Wearing blue-blocking goggles while commuting improved total sleep time (34) and sleep efficiency (35) in two studies.…”