Morning and evening salivary melatonin, sleepiness and chronotype: A comparative study of nurses on fixed day and rotating night shifts

Abstract

To compare morning and evening salivary melatonin levels, sleep quality and chronotype between nurses working fixed day shifts and those working rotating night shifts. Rotating night shift work is an inevitable part of nursing and is a major reason for disrupted sleep. Cross-sectional comparative design. We used cluster sampling to recruit 520 female nurses working fixed day and rotating night shifts in the United Arab Emirates. Morning and evening melatonin were measured from corresponding saliva samples. The Pittsburgh Sleep Quality Index used to evaluate sleep quality and self-assessment of preferred circadian times was used to assess participants' chronotypes. Data were collected between October 2017-December 2018. Rotating night shift nurses had significantly lower evening melatonin compared with the fixed day shift group. No significant difference was found in sleep quality between the groups, although more participants in the rotating night shift group (N=110, 42.31%) expressed better sleep quality than those in the fixed day group (N=90, 36.00). Participants in the rotating night shift group expressed better subjective sleep, longer sleep duration, less disturbed sleep and better daily function (p>.05) than the fixed day group. Rotating night shift participants were more likely to have evening or intermediate chronotypes and more likely to report alignment of shift work to their chronotype compared with fixed day shift participants (p=.001). Longer shift duration, marital status and city location were associated with reduced evening melatonin among nurses on rotating night shifts. Rotating night shift nurses showed evidence of better sleep than those from the fixed day shift. Proper shift assignment, chronotype and alignment with shift work appeared to produce better sleep quality. Organizational policy must consider a novel model for work schedules that allow adequate off-duty days for sleep recovery among nurses.