Prevalence of Probable Shift Work Disorder in Non-Standard Work Schedules and Associations with Sleep, Health and Safety Outcomes: A Cross-Sectional Analysis

Occupational and Driving Challenges Within Sleep Medicine

Shift work is a necessity for a society that requires 24/7 services. However, working around the clock can cause a misalignment with our sleep-wake cycle, resulting in sleepiness, impaired cognition and poor health. Due to the prevalence of shift work within safety-critical contexts, there is a need to further understand the causes and consequences of non-typical work on sleep, wellbeing, health and safety, as well as ways to effectively reduce this risk. Furthermore, disorders such as obstructive sleep apnoea, which is the most prevalent medical cause of sleepiness, compound the adverse health and safety consequences of shift work. This article provides an overview of some of the key occupational and sleep health challenges related to shift work: accurate measurement of sleepiness, mitigation, long-term sustainability and work/life balance. We conclude by proposing four directions for future work in this area to consider, with the overall aim of improving the sleep, health and wellbeing of the shift-working population.

Identifying Risk and Protective Factors for Shift Work Sleep Disorder: Insights from UK Biobank Night Shift Workers

Shift Work Sleep Disorder (SWSD) is a significant and highly prevalent condition affecting up to 48% of individuals with irregular work schedules. The diagnostic criteria for SWSD include persistent insomnia or sleepiness in relation to shift work, not attributable to other disorders or external factors. To explore risk factors of SWSD, we conducted a cross-sectional analysis among 10,787 night shift workers in the UK Biobank. To determine correlates of SWSD using multivariable-adjusted logistic regression models, a preselection of potential risk factors was made on the basis of previous literature. Self-identifying as 'Asian or Asian British' or 'Black or Black British' (compared to being 'White'), male sex, and high scores on sociability, warmth and diligence were associated with lower odds for SWSD. We did not find significant associations of chronotype, frequency of alcohol intake, smoking, and time employed in current job with SWSD. These findings underscore the need for targeted interventions and workplace policies to mitigate the adverse effects of SWSD. Future research should aim to explore the mechanisms behind these associations and develop strategies to enhance shift work tolerance among night shift workers.

The moderating role of protective factors in shift work disorder and health outcomes: A cross-sectional study

This study investigated whether sleep-specific (e.g. chronotype) and traditional (e.g. resilience) protective factors were associated with reduced shift work disorder (SWD) risk and explored their role as moderators in the relationship between SWD risk and health. Shift workers (n = 126) participated in a cross-sectional study evaluating SWD risk (i.e. low vs. high; SWD-screening Questionnaire), mental health (Patient Health Questionnaire-9; Generalized Anxiety Disorder Questionnaire-7), physical health (Subjective Health Complaints Inventory), sleep (Pittsburgh Sleep Quality Index; Insomnia Severity Index; Epworth Sleepiness Scale), and protective factors (Resilience Scale; Social Provisions Scale; Survey of Perceived Organizational Support; Short Impulsive Behavior Scale; Circadian Type Inventory; reduced-Morningness-Eveningness Questionnaire). Logistic regressions revealed lower sleep languidity was associated with reduced odds (OR = 0.88 [0.79,0.96]) for having high SWD risk. Multiple regression analyses showed in shift workers with high social support or morningness, having high SWD risk was not associated with increased depression symptoms, or insomnia severity and poor sleep quality, respectively. Finally, in those with high or medium levels of perceived organizational support, high SWD risk was not associated with increased gastrointestinal and allergy complaints. Longitudinal research with larger samples is needed to confirm the moderating role of protective factors in the relationship between SWD risk and health.

Silver Lining Study: Missileer Fatigue Mitigation During 2020 Coronavirus Pandemic

INTRODUCTION

The U.S. Air Force's Intercontinental Ballistic Missile (ICBM) force stands ready to launch weapons 365 days per year. Since its inception, missileers vigilantly operate launch consoles on a 3-day cycle: minimum 24-hour alert-shift/24-hour travel-admin/24-hour off, leading to concerns that health, morale, and alertness are chronically impacted. In 2020, a Missileer Occupational Health Assessment (OHA) revealed 76% of respondents struggle with being rested for duty and 29% of respondents never feel adequately rested for duty. Later that year, 20th Air Force initiated long-duration operations to safeguard from the SARS CoV-2 (COVID-19) Pandemic, resulting in increased operations tempo, and exacerbating crew fatigue.341st Operations Group and 341st Medical Group at Malmstrom Air Force Base enacted interventions to mitigate crew fatigue and support continued readiness during pandemic operations. They recorded, analyzed, and compiled findings in this report, including recommendations for long-term ICBM operations at Missile Wings.

MATERIALS AND METHODS

All participants were Nuclear and Missile Operations Officers, or missileers, were continuously evaluated with qualitative and quantitative measures to ensure safety of the force during a period of unprecedented change. Interventions implemented and evaluated during the 9-month period included: environmental modifications, scheduling changes, and crew education on fatigue management, nutrition, anticipatory sleep preparation, and fitness. Most notably, the 341st Operations Group examined various 3-person and 4-person shift-length and alert duration schedules. Psychomotor vigilance testing results validated safety of operators and delta between pre- and post-shift measurements. Crew force readiness trends were analyzed for force-health awareness. Pre- and post-OHA results were compared for subjective changes. Fatigue and health-related outcomes were collected from a safety monitoring effort during standard and COVID-19 operations at 341st Missile Wing.

RESULTS

Findings from qualitative and quantitative data indicate the optimal schedule is a 3-week cycle:7-day alert/7-day recovery/7-day training-administrative utilizing 4-member or 3-member crews for low tempo operations. Crews experimented with shift-lengths of 24hrs-on/24hrs-off, 16hrs-on/8hrs-off, and 12hrs-on/12hrs-off. Maximum safe alert duration is 7 days due to task fatigue onset between 8 and 10 days. Short and long duration Duties Not to Include Flight (DNIF) (also known as Duties Not to Include Alert (DNIA) among missileers) rates decreased from the first to last month of the period by 74.6% and 79.2%, respectively. The number of alerts missed per month decreased 86% from baseline. The 2021 OHA found a 7% decline in members seeking separation, and absence of sleep, fatigue, and physical or mental health as missileer concerns.

CONCLUSIONS

This analysis has identified a sustainable alert rotation of 7/7/7 with emphasis on protected recovery and training time and has been continued after concluding pandemic operations, creating consistent schedule stability where there once was none. If executed properly, this alert rotation, regardless of shift-length selected, has potential to improve trust between crews and leadership, provides adequate recovery time between alerts to maintain health, and improves wellness, family stability, morale, unit cohesion, and crew force retention. Notably, all Air Force Global Strike Missile Operations Groups adjusted scheduling practices to align with these findings.

The Development and Validation of the Health Belief Model for Shift Workers (HBM-SW) Scale

OBJECTIVE

Shift work is associated with circadian misalignment, sleep loss, and suboptimal health behaviors, which may contribute to longer term negative health outcomes. To inform future interventions for shift workers, the present study aimed to develop and evaluate the Health Belief Model for Shift Workers (HBM-SW) scale.

METHODS

The HBM-SW development involved a seven-step process, including a literature review, expert panel analysis, cognitive interviews with shift workers, and a trial with a pilot sample of shift workers (n = 153). Utilizing exploratory factor analysis for factor identification and item reduction, the developed scale loaded on seven factors in line with the theoretical framework of the Health Belief Model: Perceived Threat, Perceived Severity, Perceived Benefits, Perceived Barriers, Cues to Action, Self-efficacy, and Health Motivation. Validation of the scale was conducted utilizing Pittsburgh Sleep Quality Index, International Physical Activity Questionnaire, and Food Frequency Questionnaire.

RESULTS

The pilot sample had an average age of 34.0 (18.0) years, was majority female (54.2%), with an average of 8.0 (11.0) years shift work experience. The HBM-SW showed good - excellent (α = 0.74-0.93) internal consistency and moderate - good (ICC = 0.64-0.89) test re-test reliability. Using health behavior outcome measures, the HBM-SW scale showed meaningful correlations with sleep quality, sleep duration, diet quality and leisure time physical activity, and acceptable validity and reliability. Further testing should be conducted in a larger sample to facilitate confirmatory factor analysis.

CONCLUSIONS

The developed Health Belief Model for Shift Workers scale is likely beneficial for use in future studies of interventions for shift workers.

Diagnosis and management of sleep disorders in shift workers, with patient informed solutions to improve health services research and practice

BACKGROUND

The combination of shift work and an unmanaged sleep disorder carries health and safety risks. Yet, diagnosis rates for sleep disorders are low in shift workers. The aim of this study was to understand the experience of sleep disorder diagnosis and treatment in shift workers, and consider patient informed solutions to improve access to health services.

METHODS

Semi-structured interviews were conducted with 16 Australian shift workers with a diagnosed sleep disorder. Patient journey mapping and reflexive thematic analysis were used to understand diagnosis and management experiences.

RESULTS

There were highly variable experiences with diagnosis and management, often taking >5 years to seek help from a health care provider (HCP) after noticing symptoms of a sleep disorder. Three themes were constructed, including 'the cause of the problem', 'prioritising work', and '(dis)satisfaction and (dis)connection'. Extent of patient and HCP awareness of sleep disorders, and a prevailing attitude of shift work being 'the problem' impacted diagnosis, as did organisational needs (including rostering, which had both positive and negative influences on help seeking). Relationships with HCPs were important, and living on non-standard time was both a barrier and an enabler to sleep disorder care. Participants identified the need for education and awareness, prompts and easy access to screening and referral pathways, and tailored models of care.

CONCLUSION

Education and awareness initiatives for shift workers, their employers and HCPs, together with development of a model of care for shift workers with sleep disorders may address some of the unique barriers to diagnosis and management.

Effect of cognitive behavioral therapy for insomnia in workers: A systematic review and meta-analysis of randomized controlled trials

Although cognitive behavioral therapy for insomnia (CBT-I) is recommended as a first-line treatment, its efficacy for workers with insomnia remains unclear. This systematic review and meta-analysis aimed to determine the effectiveness of CBT-I in the management of insomnia symptoms in workers. We searched the literature in three electronic databases, namely PubMed, PsycINFO, and Embase, and included 21 studies in the meta-analysis. Compared with the control group, CBT-I overall resulted in significant improvements in terms of severity of insomnia (g = -0.91), sleep onset latency (g = -0.62), wakefulness after sleep onset (g = -0.60), early morning awakening (g = -0.58), and sleep efficiency (g = 0.71). However, there was no improvement in the total sleep time relative to that in the control group. Furthermore, CBT-I significantly alleviated depressive (g = -0.37) and anxiety (g = -0.35) symptoms and fatigue (g = -0.47) compared with the control group. Our study findings suggest that both web-based and face-to-face CBT-I are effective interventions for managing insomnia symptoms in daytime workers, although it is important to note that only face-to-face CBT-I achieved clinically meaningful changes. The effectiveness of CBT-I for shift workers could not be determined.

Insomnia and workplace productivity loss among young working adults: a prospective observational study of clinical sleep disorders in a community cohort

OBJECTIVE

To examine associations between three clinically significant sleep disorders (chronic insomnia, obstructive sleep apnoea, restless legs syndrome) and workplace productivity losses among young Australian adults.

DESIGN, SETTING

Prospective, observational study; 22-year follow-up of participants in the longitudinal birth cohort Raine Study (Perth, Western Australia).

PARTICIPANTS

Currently employed 22-year-old Raine Study participants who underwent in-laboratory sleep disorder screening for moderate to severe obstructive sleep apnoea (apnoea-hypopnea index of more than fifteen events/hour or obstructive sleep apnoea syndrome) and were assessed for insomnia and restless legs syndrome using validated measures.

MAIN OUTCOME MEASURES

Total workplace productivity loss over twelve months, assessed with the World Health Organization Health and Work Performance Questionnaire.

RESULTS

Of 1235 contactable 22-year-old Raine Study cohort members, 554 people (44.9%; 294 women [53%]) underwent overnight polysomnography, completed the baseline sleep questionnaire, and completed at least three quarterly workplace productivity assessments. One or more clinically significant sleep disorders were identified in 120 participants (21.7%); 90 participants had insomnia (17%), thirty clinically significant obstructive sleep apnoea (5.4%), and two restless legs syndrome (0.4%). Seventeen people (14% of those with sleep disorders) had previously been diagnosed with a sleep disturbance by a health professional, including fourteen with insomnia. Median total workplace productivity loss was greater for participants with sleep disorders (164 hours/year; interquartile range [IQR], 0-411 hours/year) than for those without sleep disorders (30 hours/year; IQR, 0-202 hours/year); total workplace productivity loss was 40% greater for participants with sleep disorders (adjusted incidence rate ratio, 1.40; bias-corrected and accelerated 95% confidence interval, 1.10-1.76). The estimated population total productivity loss (weighted for disorder prevalence) was 28 644 hours per 1000 young workers per year, primarily attributable to insomnia (28 730 hours/1000 workers/year).

CONCLUSION

Insomnia is a risk factor for workplace productivity loss in young workers. Tailored interventions are needed to identify and manage sleep disorders, particularly as most of the sleep disorders detected in the Raine Study had not previously been diagnosed.

The Good Sleeper Scale-15 items: a questionnaire for the standardised assessment of good sleepers

Research with 'good sleepers' is ubiquitous, yet there are no standardised criteria to identify a 'good sleeper'. The present study aimed to create and validate a questionnaire for identifying good sleepers for use in research studies known as the Good Sleeper Scale-15 items (GSS-15). Data were derived from a population-based survey of Australian adults (n = 2,044). A total of 23 items were chosen for possible inclusion. An exploratory factor analysis (EFA) was conducted on ~10% of the survey dataset (n = 191) for factor identification and item reduction. A confirmatory factor analysis (CFA) was conducted on the remaining data (n = 1,853) to test model fit. Receiver operating characteristic curves and correlations were conducted to derive cut-off scores and test associations with sleep, daytime functioning, health, and quality-of-life. The EFA identified six factors: 'Sleep Difficulties', 'Timing', 'Duration', 'Regularity', 'Adequacy', and 'Perceived Sleep Problem'. The CFA showed that model fit was high and comparable to other sleep instruments, χ² (63) = 378.22, p < 0.001, root mean square error of approximation = 0.05, with acceptable internal consistency (α = 0.76). Strong correlations were consistently found between GSS-15 global scores and outcomes, including 'a good night's sleep' (r = 0.7), 'feeling un-refreshed' (r = -0.59), and 'experienced sleepiness' (r = -0.51), p < 0.001. Cut-off scores were derived to categorise individuals likely to be a good sleeper (GSS-15 score ≥40) and those very likely to be a good sleeper (GSS-15 score ≥45). The GSS-15 is a freely available, robust questionnaire that will assist in identifying good sleepers for the purpose of sleep research. Future work will test relationships with other sleep measures in community and clinical samples.

Is cognitive behavioral therapy for insomnia (CBTi) efficacious for treating insomnia symptoms in shift workers? A systematic review and meta-analysis

Shift workers commonly report insomnia symptoms. Cognitive behavioral therapy for insomnia (CBTi) is the first line treatment for insomnia, however efficacy in shift workers is not well understood. This systematic review and meta-analysis evaluates existing trials of CBTi in shift working populations. A systematic literature search was conducted across seven electronic databases (n = 2120). Fifty-two full-text articles were reviewed and of these, nine studies (across ten publications with a total of 363 participants) were deemed suitable for inclusion. Heterogeneity was considerable between studies, with variability in study design, style and delivery of intervention, and follow-up times. Small sample sizes were common and attrition was high. Some studies modified aspects of CBTi for use in shift workers, while others were limited to psycho-education as part of larger intervention studies. Mean differences (MD) pre and post CBTi were modest for both the insomnia severity index (ISI; MD: -3.08, 95% CI: -4.39, -1.76) and the Pittsburgh sleep quality index (PSQI; MD: -2.38, 95% CI: -3.55, -1.21). Neither difference was of a magnitude considered to reflect a clinically significant improvement. Tailored approaches to CBTi are needed for shift workers to improve efficacy, ideally including co-production with workers to ensure interventions meet this population's needs.

Shift work, clinically significant sleep disorders and mental health in a representative, cross-sectional sample of young working adults

Mental health conditions confer considerable global disease burden in young adults, who are also the highest demographic to work shifts, and of whom 20% meet criteria for a sleep disorder. We aimed to establish the relationship between the combined effect of shift work and sleep disorders, and mental health. The Raine Study is the only longitudinal, population-based birth cohort in the world with gold-standard, Level 1 measurement of sleep (polysomnography, PSG) collected in early adulthood. Participants (aged 22y) underwent in-laboratory PSG and completed detailed sleep questionnaires. Multivariable adjusted robust linear regression models were conducted to explore associations with anxiety (GAD7) and depression (PHQ9), adjusted for sex, health comorbidities, and work hours/week. Data were from 660 employed young adults (27.3% shift workers). At least one clinically significant sleep disorder was present in 18% of shift workers (day, evening and night shifts) and 21% of non-shift workers (p = 0.51); 80% were undiagnosed. Scores for anxiety and depression were not different between shift and non-shift workers (p = 0.29 and p = 0.82); but were higher in those with a sleep disorder than those without (Md(IQR) anxiety: 7.0(4.0-10.0) vs 4.0(1.0-6.0)), and depression: (9.0(5.0-13.0) vs 4.0(2.0-6.0)). Considering evening and night shift workers only (i.e. excluding day shift workers) revealed an interaction between shift work and sleep disorder status for anxiety (p = 0.021), but not depression (p = 0.96), with anxiety scores being highest in those shift workers with a sleep disorder (Md(IQR) 8.5(4.0-12.2). We have shown that clinical sleep disorders are common in young workers and are largely undiagnosed. Measures of mental health do not appear be different between shift and non-shift workers. These findings indicate that the identification and treatment of clinical sleep disorders should be prioritised for young workers as these sleep disorders, rather than shift work per se, are associated with poorer mental health. These negative mental health effects appear to be greatest in those who work evening and/or night shift and have a sleep disorder.

Night shift work and depression among Chinese workers: the mediating role of sleep disturbances

BACKGROUND

Depression is considered as a global problem. Recently, the prevalence of depression among night shift workers has been attracting people's attention. This study aims to explore the associations among night shift work, shift frequency and depression among Chinese workers and to explore whether sleep disturbances are a critical factor.

METHODS

The cross-sectional survey consists of 787 autoworkers from a manufacturing plant in Fuzhou, China. Information about night shift work, shift frequency, depression, and sleep disturbances were collected from work records and responses to the Patient Health Questionnaire (PHQ-9) and the Pittsburgh Sleep Quality Index (PSQI). A mediation model was generated to examine relationship between night shift work, sleep disturbances, and depression.

RESULTS

Our results found that night shift work, shift frequency, sleep disturbances, and depression had positive and significant relationships in a sample of Chinese workers. Night shift work, shift frequency and sleep disturbances were associated with an increased risk of depression among workers (OR: 4.23, 95% CI 2.55-7.00; 3.91, 2.31-6.63; 6.91, 4.40-10.86, respectively). Subsequent mediation analysis found that the association between night shift work and depression appeared to be partially mediated by sleep disturbances.

CONCLUSION

These findings suggest that appropriate intervention and management strategies should be considered to alleviate the mental health burden of night shift workers.

Longitudinal studies of sleep, physical activity and nutritional intake in shift workers: A scoping review

Shift work is known to be associated with poor health outcomes, however our understanding of health behaviours (sleep, physical activity and nutritional intake) longitudinally in shift workers is currently limited. Systematic searches of four data bases were conducted. Using PRISMA-ScR guidelines we report a scoping review of 15 eligible studies. Of the included studies, 11 studies examined sleep outcomes, three examined physical activity and two examined nutritional intake. The number of follow ups conducted in each study varied from one to six, with the majority of studies reporting one follow up. Study length varied from six months to 16 years. Findings suggest that shift workers have stable but largely insufficient sleep longitudinally. Many shift workers, particularly inexperienced shift workers, are additionally experiencing poor sleep quality. There is limited data longitudinally on physical inactivity and nutrition intake, but included studies indicate that shift workers may also be physical inactive and with some poor nutritional intake (i.e., high levels of saturated fat intake). Longitudinal studies of shift work with multiple follow-ups are needed to address the current gaps in literature. The evidence that shift workers may be susceptible to poor health behaviours longitudinally is important as it provides a means by which strategies and interventions can be targeted, at both individual and organisational levels, to assist in better long term health outcomes.

Insomnia Prevalence Varies with Symptom Criteria Used with Implications for Epidemiological Studies: Role of Anthropometrics, Sleep Habit, and Comorbidities

Introduction

Estimating insomnia prevalence in epidemiological studies is hampered by variability in definitions and interpretation of criteria. We addressed the absence of a population-based estimate of insomnia in Australia using the widely accepted contemporary International Classification of Sleep Disorders (ICSD-3) criteria, which includes sleep opportunity, and has not been applied in studies to date. Consistent use of these criteria across epidemiological studies, however, requires evidence of the clinical utility of a sleep opportunity criterion for targeting strategies.

Methods

A cross-sectional national on-line survey (2019 Sleep Health Foundation Insomnia Survey) of Australian adults (18-90 years, n = 2044) was conducted. Chronic insomnia was defined as sleep symptoms and daytime impairment experienced ≥3 times per week, and present for ≥3 months, with adequate sleep opportunity (time in bed (TIB) ≥7.5 hrs). Self-rated general health (SF-1) and ever diagnosed health conditions (including sleep disorders) were assessed.

Results

Chronic difficulties initiating and maintaining sleep and daytime symptoms (n = 788) were more common in females (41.5%) than males (35.3%), p = 0.004. Excluding participants reporting frequent pain causing sleep disruption and TIB <7.5 hrs generated an insomnia disorder estimate of 25.2% (95% CI: 22.5-28.2) in females and 21.1% (18.4-23.9) in males [23.2% (21.2-25.2) overall]. This compares with 8.6% (7.3-10.0) with insomnia symptoms and TIB <7.5 hrs and 7.5% (6.4-8.7%) ever diagnosed with insomnia. Insomnia symptom groups with TIB <7.5 and ≥7.5 hours demonstrated similar odds of reporting fair/poor health [odds ratio (OR): 3.2 (95% CI: 2.1-4.8) and 2.9 (95% CI: 2.2-3.9) respectively], ≥1 mental health condition, ≥1 airway disease, and multimorbidity.

Conclusion

Adults with significant sleep and daytime symptomatology and TIB <7.5 hrs did not differ clinically from those with insomnia disorder. Consideration of criteria, particularly adequate sleep opportunity, is required to consistently identify insomnia, and establish health correlates in future epidemiological studies. Further evaluation of the clinical utility of the sleep opportunity criterion is also required.

Shift work disorder and the prevalence of help seeking behaviors for sleep concerns in Australia: A descriptive study

Shift work disorder (SWD) is a circadian rhythm sleep-wake disorder, defined by symptoms of insomnia and excessive levels of sleepiness resulting from work that occurs during non-standard hours. Sleep problems are common in shift workers, yet our understanding of help seeking behaviours for sleep in shift workers is limited. The primary aim of this study was to examine the help seeking behaviours of Australian workers who meet criteria for SWD. Of the 448 (46% of sample, n = 964 total) Australian workers reporting non-standard work hours, 10.5% (n = 41) met the criteria for probable shift work disorder (pSWD). Non-standard workers with pSWD did not seek help for sleep problems at higher rates than workers without SWD. Of the small proportion of workers with pSWD who sought help, general practitioners were the most common healthcare professionals for sleep problems. Self-management was common in workers with pSWD, with a high self-reported prevalence of alcohol use (31.7%) as a sleep management strategy, and caffeine consumption (76.9%) as a sleepiness management strategy. The majority of individuals with pSWD reported the mentality of 'accept it and keep going' as a sleepiness management strategy, highlighting a potential barrier to help seeking behaviour in workers with pSWD. These findings provide novel insight into the help seeking behaviours of those with pSWD. There is a need for further research to understand why individuals at risk for SWD are not actively seeking help, and to develop health promotion and intervention strategies to improve help seeking when needed.

Who is 'on-call' in Australia? A new classification approach for on-call employment in future population-level studies

BACKGROUND

On-call research and guidance materials typically focus on 'traditional' on-call work (e.g., emergency services, healthcare). However, given the increasing prevalence of non-standard employment arrangements (e.g., gig work and casualisation), it is likely that a proportion of individuals who describe themselves as being on-call are not included in current on-call literature. This study therefore aimed to describe the current sociodemographic and work characteristics of Australian on-call workers.

METHODS

A survey of 2044 adults assessed sociodemographic and work arrangements. Of this population, 1057 individuals were workforce participants, who were asked to provide information regarding any on-call work they performed over the last three months, occupation type, weekly work hours, and the presence or absence of non-standard work conditions.

RESULTS

Of respondents who were working, 45.5% reported working at least one day on-call in the previous month. There was a high prevalence of on-call work in younger respondents (63.1% of participants aged 18-24 years), and those who worked multiple jobs and more weekly work hours. Additionally, high prevalence rates of on-call work were reported by machinery operators, drivers, community and personal service workers, sales workers, and high-level managers.

CONCLUSIONS

These data suggest that on-call work is more prevalent than previously recorded and is likely to refer to a broad set of employment arrangements. Current classification systems may therefore be inadequate for population-level research. A taxonomy for the classification of on-call work is proposed, incorporating traditional on-call work, gig economy work, relief, or unscheduled work, and out of hours work.