The effects of different roster schedules on sleep in miners

Shiftwork involving early morning starts and night work can affect both sleep and fatigue. This study aimed to assess the impact of different rostering schedules at an Australian mine site on sleep and subjective sleep quality

Performance on a simple response time task : is sleep or work more important for miners?

The purpose of the current study was to investigate the impact of work- and sleep-related factors on an objective measure of response time in a field setting

The relative contributions of the homeostatic and circadian processes to sleep regulation under conditions of severe sleep restriction

Study Objectives: To investigate the relative contributions of the homeostatic and circadian processes on sleep regulation under conditions of severe sleep restriction. Design: The 13-day laboratory based study consisted of 3 x 24-h baseline days (8 h sleep opportunity, 16 h wake) followed by 7 x 28-h forced desynchrony days (4.7 h sleep opportunity, 23.3 h wake). Setting: The study was conducted in a time isolation unit at the Centre for Sleep Research, University of Australia. Participants: Fourteen healthy, nonsmoking males, aged 21.8 SD) years participated in the study. Interventions N/AMeasurements: Sleep was measured using standard polysomnography. Core body temperature (CBT) was recorded and continuously using a rectal termistor. Each epoch of sleep was assigned a circadian phase based on the CBT data (6 x 60-degree bins) and an elapsed time into sleep episode (2 x 140-min intervals). Results: The percentage of SWS decreased with elapsed time into the sleep episode. However, no change in the percentage of REM sleep was observed with sleep progression. Whilst there was a circadian modulation of REM sleep, the amplitude of the circadian variation was smaller than expected. Sleep efficiency remained high throughout the sleep episode and across all circadian phases.Conclusions: Previous forced desynchrony studies have demonstrated a strong circadian influence on sleep, in the absence of sleep restriction. The current study suggests that in the presence of high homeostatic pressure, the circadian modulation of sleep, in particular sleep efficiency and to a lesser extent, REM sleep, are reduced

The influence of break timing on the sleep quantity and quality of fly-in, fly-out shiftworkers

Abstract: Although shift and break timing is known to affect the sleep of shiftworkers, this has not been demonstrated in Fly-in, Fly-out (FIFO) settings which, compared to residential based settings, may be favourable for sleep. This study investigated the sleep quantity and quality of shiftworkers working a FIFO operation comprising of shifts, and therefore breaks, across the 24-h day. The sleep of 24 males (50.43 ± 8.57 yr) was measured using actigraphy and sleep diaries. Morning breaks were associated with less sleep (09:00–12:00 h; 4.4 ± 1.3 h) and a poorer sleep quality (06:00–09:00 h; 3.1 ± 1.0, “average”) compared to breaks beginning between 00:00 h and 03:00 h (6.8 ± 1.7 h; 2.2 ± 0.9, “good”). Sleep efficiency remained constant regardless of break timing (85.9 ± 5.0% to 89.9 ± 3.5%). Results indicate that even in operations such as FIFO where sleeping conditions are near- optimal and the break duration is held constant, the influence of the endogenous circadian pace- maker on sleep duration is evident

The influence of circadian time and sleep dose on subjective fatigue ratings

Subjective ratings of fatigue are increasingly being used as part of a suite of tools to assess fatigue-related risk on the road and in the workplace. There is some debate however, as to whether individuals can accurately gauge their own fatigue states, particularly under conditions of sleep restriction. It is also unclear which references are used by individuals to assess fatigue – for example prior sleep, time of day, workload, or previous ratings. The current study used a sophisticated laboratory protocol to examine the independent contributions of sleep, circadian phase and sleep debt to fatigue ratings. Importantly, participants had no knowledge of time of day, how much sleep they were getting, or how long they were awake. Twenty-eight healthy, young males participated in one of two conditions of a 28 h forced desynchrony protocol – severe sleep restriction (4.7 h sleep and 23.3 h wake) or moderate sleep restriction (7 h sleep and 21 h wake). Fatigue ratings were provided prior to and following each sleep period using the Samn–Perelli fatigue scale. Repeated measures ANOVAs were used to analyse the effects of circadian phase, sleep dose and study day. Results demonstrated an effect of circadian phase on both pre-sleep and post-sleep fatigue ratings. The significant effect of study day is interpreted as an effect of circadian time, as opposed to accumulating sleep debt. An effect of sleep dose was only seen in post-sleep fatigue ratings. The findings suggest that post-sleep fatigue ratings may be sensitive to prior sleep and may be useful as an indicator of fatigue-related risk, particularly when triangulated with information about recent total sleep time

A 28 hour day, sleep and single beat period : revisiting forced desynchrony studies?

Eleven healthy males lived in a time isolation unit for 12 days to assess the effects of the homeostatic and circadian processes on sleep architecture over a single beat period. Participants were scheduled to seven 28h experimental days (9.3h sleep, 18.7h wake) with sleep periods occurring at varying times across the endogenous circadian cycle. Results demonstrate the circadian and homeostatic influences on sleep architecture are detectable over a single beat period. Future studies looking at the effects and interactions of the circadian and homeostatic processes on sleep may not require the use of more than one beat period