BACKGROUND: Morningness and eveningness preference (chronotype), an endogenous component of the circadian clock could play a key role in a worker's ability for adjusting to shift work. Morning types are those individuals who prefer going to bed and waking up early, whereas Evening types tend to sleep at later hours and find it difficult to get up in the morning.
OBJECTIVE: The objective of this study was to survey, the relationship between morningness-eveningness type, sleep quality and insomnia in shift worker nurses.
PARTICIPANTS: The participants comprised 160 nurses working in three different wards in two university hospitals in Iran.
METHODS: Nurses completed the Horne and Ostberg questionnaire to assess the distribution of morningness or eveningness preference, the Pittsburg Sleep Quality Index and Insomnia Severity Index questionnaire to measure self reported sleep quality and insomnia. Demographic information was also collected in order to explore the relationship between circadian rhythms, sleep quality and prevalence of insomnia in shift workers.
RESULTS: The results showed that the prevalence of poor sleep quality was high. More than half of the participants had poor sleep. Evening type nurses had worse sleep quality in our study (P < 0.05). There is not any significant association between the shift type and age of the nurses with their quality of sleep (P > 0.05).
CONCLUSIONS: The results suggested that nurses who had a morning sleep preference had better sleep quality. A survey of chronotype of nurses could be useful, so that individuals may be assigned to different shifts according to their sleep preference.
