Effects of a reduction in the number of short intervals between work shifts on heart rate variability: A prospective field study of female nurses

Abstract

Introduction: Shift work is one of the most serious occupational risk factors for health problems such as cardiovascular diseases. Furthermore, shift work disturbs sleep and alertness and impairs recovery from work, especially if the time between work shifts is insufficient. The aim of this study was to evaluate if a reduced number of short intervals (i.e., less than 11 hours) between work-shifts would result in better recovery indicated by sleep time heart rate variability reflecting the psychophysiological recovery.
Methods: Participants were 39 female shift-working nurses with the mean age of 45 years. The study design was a prospective within-subject study with a one year follow-up. The 24-hour heart rate variability recordings supplemented with questionnaires were performed twice. First, while working in the old shift schedule with frequent short intervals between work shifts, and again after one year of a working schedule with a reduced number of short intervals between work shifts. Statistical analyses were conducted using liner mixed models.
Results: The comparison between the initial shift system and the schedule with the reduced number of short intervals between work shifts caused an increase in heart rate variability parameters reflecting mainly parasympathetic activation of the autonomic nervous system (i.e., RMSSD, HF power and HF power in normalized units) (p < .001).
Conclusions: In conclusion, our results suggest that reducing the number of short intervals between work shifts is an effective way to enhance the physiological recovery during the sleep. This study demonstrated that the recovery of autonomic nervous system from shift work can be promoted by implementation of ergonomic recommendations.