The aim of this longitudinal study on novice police officers was to investigate inter-individual differences in sleep response to shift work, and to identify potential baseline predictors thereof. A total of 42 subjects were assessed at baseline, prior to commencing shift work. They were re-assessed during three follow-up sessions within the first 2 years of shift work exposure after approximately 4, 12, and 20 months of rotating shift work. Wrist actigraphy and sleep logs were used to investigate nocturnal sleep at baseline and daytime sleep after night shifts during the follow-up sessions. Actigraphically estimated total sleep time and subjective sleep quality were analyzed as outcome variables, using mixed-effects analysis of variance. Systematic inter-individual differences were observed in the overall response of these outcome variables to shift work. In this sample, flexibility of sleeping habits and gender were found to be predictors of daytime total sleep time in the first 2 years of shift work exposure. Flexibility of sleeping habits and subjective quality of nighttime sleep prior to shift work were found to be predictors of subjective quality of daytime sleep. These results suggest that it may be possible to detect and even predict sleep deficiencies in response to shift work early on, which could be a basis for the development of individualized interventions to improve shift work tolerance.
Keywords: Police; predictors; shift work; shift work tolerance; sleep duration; subjective sleep quality; systematic inter-individual differences; wrist actigraphy.