Individual differences in night and continuously-rotating shiftwork: seeking anticipatory rather than compensatory strategy

Sleep-Scheduling Strategies in Hospital Shiftworkers

INTRODUCTION

Shiftwork causes circadian disruption and results in impaired performance, sleep, and health. Often, individuals on non-standard shifts cannot modify work schedules. At-home sleep schedules are a potentially modifiable point of intervention, yet sleep-scheduling strategies remain relatively understudied. Specifically, the adoption of multiple strategies and the employment of strategies for not only night shifts, but also early starts on days, have yet to be formally examined to our knowledge. We studied how adoption of specific and/or multiple sleep-scheduling strategies for day and night shifts relates to measures of adaptation to shiftwork, self-reported on-shift sleepiness, and individual characteristics (eg, age, chronotype, education in circadian and sleep health). We hypothesized: 1) strategies would differ by shift type, 2) individuals would adopt multiple strategies, 3) strategies better aligned with circadian principles would relate to measures of adaptation, and 4) individual characteristics, such as having dependents, would relate to strategy selection.

METHODS

A retrospective, online questionnaire (including items from the Survey of Shiftworkers and items related to sleep-scheduling strategies) was administered to both permanent and rotating hospital staff in four wards working 12-h day and/or night shifts (n=89). Additionally, reasons for strategy selection were explored.

RESULTS

Level of adaptation varied by sleep-scheduling strategy, with the least adaptation for those utilizing the Incomplete Shifter strategies. For night shifts, Night Stay and Switch Sleeper-N strategies were related to lower mid-shift sleepiness. Many night workers reported using strategies that restricted sleep, and most reported using multiple strategies, both of which also related to lower adaptation. Domestic considerations were the most common rationale for strategy selection. Strategies varied by several individual characteristics, including chronotype, dependents, and level of sleep education.

DISCUSSION

Future work should investigate sleep strategies and circadian interventions to help mitigate the effects of circadian and sleep disruption in hospital staff.

A model of shiftworker sleep/wake behaviour

Software-based biomathematical models of alertness provide a means to estimate fatigue-related risk in advance of a schedule being worked. Obtaining a good estimate of employees' sleep/wake behaviour during non-work periods is critical in obtaining accurate estimates of alertness. This is because estimates of alertness are generated based on estimated sleep and wake times, not rest and work times per se. The purpose of the current analysis was to evaluate the predictive validity of a novel version of a previously published sleep predictor model. This model was originally designed to predict sleep probability for aviation pilots in connection with long-haul flight operations. It has since been modified to predict sleep periods for industrial shiftwork rosters in non-transmeridian environments. The algorithm uses two procedures to predict sleep timing and duration: (1) estimate the total amount of sleep likely to be obtained in a given rest period; and then (2) estimate the timing and duration of sleep periods within that rest period. The sleep periods predicted in the second procedure are generated such that their combined sum is a priori equivalent to the total amount of sleep predicted in the first procedure. The model was parameterized and validated based on a sample of 225 train drivers who collected work/rest and sleep/wake data for two weeks during normal commercial operations. Agreement between observed and predicted sleep periods was robust (percent agreement=85%) and compared favourably with agreement levels between sleep behaviours exhibited by the same individual on distinct occasions but where shift sequences were repeated. These results are discussed within the context of ongoing efforts to develop individualized biomathematical models of alertness.

Prediction of probabilistic sleep distributions following travel across multiple time zones

STUDY OBJECTIVES

To parameterize and validate a model to estimate average sleep times for long-haul aviation pilots during layovers following travel across multiple time zones. The model equations were based on a weighted distribution of domicile- and local-time sleepers, and included algorithms to account for sleep loss and circadian re-synchronization.

DESIGN

Sleep times were collected from participants under normal commercial operating conditions using diaries and wrist activity monitors.

PARTICIPANTS

Participants included a total of 306 long-haul pilots (113 captains, 120 first officers, and 73 second officers).

MEASUREMENT AND RESULTS

The model was parameterized based on the average sleep/wake times observed during international flight patterns from Australia to London and Los Angeles (global R2 = 0.72). The parameterized model was validated against the average sleep/wake times observed during flight patterns from Australia to London (r2 = 0.85), Los Angeles (r2 = 0.79), New York (r2 = 0.80), and Johannesburg (r2 = 0.73). Goodness-of-fit was poorer when the parameterized model equations were used to predict the variance across the sleep/wake cycles of individual pilots (R2 = 0.42, 0.35, 0.31, and 0.28 for the validation flight patterns, respectively), in part because of substantial inter-individual variability in sleep timing and duration.

CONCLUSIONS

It is possible to estimate average sleep times during layovers in international patterns with a reasonable degree of accuracy. Models of this type could form the basis of a stand-alone application to estimate the likelihood that a given duty schedule provides pilots, on average, with an adequate opportunity to sleep.

Efficacy and hypnotic effects of melatonin in shift-work nurses: double-blind, placebo-controlled crossover trial

Background

Night work is associated with disturbed sleep and wakefulness, particularly in relation to the night shift. Circadian rhythm sleep disorders are characterized by complaints of insomnia and excessive daytime sleepiness that are primarily due to alterations in the internal circadian timing system or a misalignment between the timing of sleep and the 24-h social and physical environment.

Methods

We evaluated the effect of oral intake of 5 mg melatonin taken 30 minutes before night time sleep on insomnia parameters as well as subjective sleep onset latency, number of awakenings, and duration of sleep. A double-blind, randomized, placebo-controlled crossover study with periods of 1 night and washouts of 4 days comparing melatonin with placebo tablets was conducted. We tried to improve night-time sleep during recovery from night work. Participants were 86 shift-worker nurses aged 24 to 46 years. Each participant completed a questionnaire immediately after awakening.

Results

Sleep onset latency was significantly reduced while subjects were taking melatonin as compared with both placebo and baseline. There was no evidence that melatonin altered total sleep time (as compared with baseline total sleep time). No adverse effects of melatonin were noted during the treatment period.

Conclusion

Melatonin may be an effective treatment for shift workers with difficulty falling asleep.

Estudo do cronótipo de um grupo de trabalhadores em turnos

Neste estudo, os objetivos foram descrever as características de matutinidade/vespertinidade de um grupo de trabalhadores em turnos de uma indústria química e identificar possíveis associações entre cronótipo e turno de trabalho. A pesquisa foi realizada em uma indústria química do interior do estado de São Paulo. Os trabalhadores lotados nesta seção eram distribuídos em dois turnos: matutino e vespertino. A amostra constituiu-se de 44 trabalhadores, dos sexos feminino e masculino, que trabalhavam em ambos os turnos. Os dados foram coletados com a versão brasileira do questionário de identificação de indivíduos matutinos e vespertinos que foi elaborado por Horne & Östberg (1976). Foi verificado o predomínio do cronótipo "moderadamente matutino" - MM (n = 21 ou 47,73%) -, seguido pelo tipo "Indiferente" - IN (n = 12 ou 27,27%) - e pelo tipo "definitivamente matutino" - DM (n = 10 ou 22,73%). Somente um indivíduo foi classificado como "definitivamente vespertino" - DV (2,27%). Entre os trabalhadores estudados houve predomínio do cronótipo "moderadamente matutino" seguido do tipo "indiferente" e do tipo "definitivamente matutino". Não foram verificadas associações estatisticamente significativas entre o cronótipo e as características individuais neste estudo.

A saúde do trabalhador na sociedade 24 horas

Este artigo trata, em um primeiro momento, de fatores subjacentes às diferenças individuais quanto à tolerância ao trabalho em turnos e noturno. Associadas a esses fatores, também são apresentadas características do trabalho que podem ou não favorecer a tolerância ao trabalho em turnos. Em um segundo momento, apresenta-se medidas de intervenção que visam minimizar as dificuldades enfrentadas pelos trabalhadores quanto à saúde e ao bem-estar orgânico e social.

Sleep quality and responses to insufficient sleep in women on different work shifts

1. The aim of this study was to examine degrees of cognitive behavioural effects of fatigue, mood changes and somatic responses to sleep loss in women with and without sufficient sleep, and to explore possible links between effects of sleep loss and specific sleep disturbances in selected groups. 2. A total 156 women working in a casualty department on different work shifts responded to a questionnaire which measured sleep quality, strain and symptoms related to working conditions, as well as effects of sleep loss. 3. About 40% of the women had perceived insufficient sleep during the last 6 months. They perceived significantly worse sleep quality and a higher degree of strain according to working conditions than the others. Palpitation and dysphoria as effects of sleep loss were independently predicted by sleep quality. Dysphoria was also predicted by difficulty in falling asleep. Cognitive behavioural effects of fatigue was predicted by disturbed sleep. Palpitation effects led to a 10-fold increase in the probability of cognitive behavioural effects of fatigue. The effects were most prominent among women suffering from gastrointestinal problems of long duration and chronic pain. 4. Responses to reduced sleep quality in women constitute a form of stress, with sympathetic activation, increased susceptibility to infection, moderate cognitive impairment, mood changes and somatic distress.