Circadian Adaptation to Night Shift Work Influences Sleep, Performance, Mood and the Autonomic Modulation of the Heart

Abstract

Our aim was to investigate how circadian adaptation to night shift work affects psychomotor performance, sleep, subjective alertness and mood, melatonin levels, and heart rate variability (HRV). Fifteen healthy police officers on patrol working rotating shifts participated to a bright light intervention study with 2 participants studied under two conditions. The participants entered the laboratory for 48 h before and after a series of 7 consecutive night shifts in the field. The nighttime and daytime sleep periods were scheduled during the first and second laboratory visit, respectively. The subjects were considered “adapted” to night shifts if their peak salivary melatonin occurred during their daytime sleep period during the second visit. The sleep duration and quality were comparable between laboratory visits in the adapted group, whereas they were reduced during visit 2 in the non-adapted group. Reaction speed was higher at the end of the waking period during the second laboratory visit in the adapted compared to the non-adapted group. Sleep onset latency (SOL) and subjective mood levels were significantly reduced and the LF∶HF ratio during daytime sleep was significantly increased in the non-adapted group compared to the adapted group. Circadian adaptation to night shift work led to better performance, alertness and mood levels, longer daytime sleep, and lower sympathetic dominance during daytime sleep. These results suggest that the degree of circadian adaptation to night shift work is associated to different health indices. Longitudinal studies are required to investigate long-term clinical implications of circadian misalignment to atypical work schedules.

Safety and acceptability of an organic light-emitting diode sleep mask as a potential therapy for retinal disease

“…15 The effect of this wavelength on the melanopsin containing retinal ganglion cells responsible for circadian synthesis could suppress and shorten melatonin onset and duration, and potentially impact sleep, thermoregulation, blood pressure, and glucose homeostasis. 16,17 Sleep disturbance and intolerance to light appeared to be the principal reasons given for withdrawal, especially in older volunteers; in younger people withdrawal was associated with lack of compliance with mask wear and/or attendance. The level of light intolerance of 5-10% appears acceptable as light therapy moves into efficacy trials.…”

Association between light exposure at night and insomnia in the general elderly population: The HEIJO-KYO cohort

“…Physiologically, light exposure is the most important environmental entraining cue for SCN function. Chronic circadian misalignment between the internal and environmental rhythms, which is typically related to night-shift work and clock-gene variants, is associated with disruption of SCN function and increased risk of insomnia (Allebrandt et al, 2010;Boudreau et al, 2013;Wyatt et al, 1999). Melatonin, a pineal gland hormone, is hypothesized to be a major internal contributor to the association between circadian misalignment and insomnia because endogenous melatonin levels are closely associated with both light exposure and sleepiness (Dijk & Cajochen, 1997;Zeitzer et al, 2000).…”

Association Between Sleep Quality and Subjective Fatigue in Night-Shift Nurses with Good and Poor Sleep

“…Individual differences in adaptation to rotational-shift work have been reported, and several studies have examined the effects of this adaptation on circadian phase, sleep quality, work performance, and the endocrine system in rotational-shift workers [16][17][18][19][20][21]. In addition, differences in adaptation and sleep status have been reported in nurses who work night shift [22,23], and the severity of sleep problems during adaptation was attributed to accumulative subjective fatigue [22].…”