Investigation of the relationship between sleep problems and work injuries

BACKGROUND Work injuries are a major problem worldwide. Approximately 360,000 fatal occupational injuries occur yearly, and more than 960,000 workers are injured daily. The worldwide estimated cost of work injuries is over US$ 400 billion a year. In Switzerland, the number of work injuries recognised by the Swiss National Accident Insurance Institution has remained stagnant at approximately 95 work injuries per 1,000 full-time employees annually, after a decrease in work injuries in the decade before. The stagnation of the decrease and the middle rank for work injury risk in the European comparison has resulted in a demand for revising prevention measures. A preliminary literature search on potentially important but disregarded causes of work injuries revealed that little is known about the personal factors influencing work injuries and that sleep problems may be a relevant but underestimated risk for work injury. Sleep problems are one of the most common health complaints with a varying prevalence of up to 40 % depending on the sleep problem type and examination method. Sleep problems may constrict the recovery function of sleep and lead to sleepiness during the day. Sleepiness may in turn reduce work performance and increase the risk of work injury. The role of sleep as a potential risk factor in injury prevention is still under debate. The strong belief and consensus among specialists that sleep problems have an impact on the incidence of work injuries has never been approached systematically and pooled quantitatively. No data from Switzerland are currently available on this topic. Furthermore, it is unclear whether sleep quality, sleep duration and daytime sleepiness influence the various types of work injuries differently. Additionally, limited and conflicting evidence is available on factors that modify the relationship between sleep problems and work injuries. OBJECTIVES Derived from the above knowledge gaps and research needs, the overall aims of this thesis were to (i) better understand the influence of sleep problems on work injuries, (ii) identify susceptible types of work injuries and populations most at risk and (iii) investigate whether our international findings can be verified for Switzerland. METHODS The research questions of this thesis were addressed in the framework of two separate study parts. First, a systematic literature review was performed consisting of a search of several databases. Original articles quantifying the relationship between sleep problems and work injuries were included up to July 7th, 2011. Pooled relative risks expressed in odds ratios (OR) and 95 % confidence intervals (CI) were calculated through random effects models. Several subgroup meta-analyses and meta-regression analyses were performed, and the population attributable risk was estimated. Second, a case-control study including 180 cases and 551 controls was conducted at the University Hospital of Basel, Switzerland, from December 1st 2009 to June 30th, 2011. Work injuries were defined according to Swiss law. Data on sleep problems were collected using the validated German versions of the Pittsburgh Sleep Quality Index (PSQI) and the Epworth Sleepiness Scale (ESS). The potential confounders considered included socioeconomic, health, lifestyle, occupational and environmental factors. Data analysis was performed in two steps; work injuries were investigated first, and then, we analysed the full case-control sample. RESULTS Through the systematic review, we identified 27 studies reporting 54 estimates for the relationship between sleep problems and work injuries. Meta-analysis suggested that sleep problems significantly increased the risk of suffering a work injury by 62 % (OR = 1.62, 95 % CI 1.43 – 1.84). Approximately 13 % of the work injuries were attributed to sleep problems. Subgroup meta-analysis showed that every type of sleep problem was significantly related to work injury; the highest risks were observed for taking sleep medication and breathing related sleep problems. Sleep problems tended to increase the work injury severity. Additionally, work injury risks tended to be higher in workers with more severe sleep problems. Findings from the case-control study suggested that workers with poor sleep quality had a 78 % (OR = 1.78, 95 % CI 1.01 – 3.17) higher risk of being injured at work than workers with good sleep quality. More severe sleep problems were associated with a higher work injury risk, and having sleep problems resulted in a greater history of work injuries, independent of case status. The analysis of the work injury data revealed that the work injury types most susceptible to sleep problems were falls and musculoskeletal injuries, injuries while working with or being injured by a tool or machine, and injuries while performing a side task. Sleep quality, sleep duration and daytime sleepiness were significant risk factors for at least one type of work injury. The populations identified as most at risk for sleep problem related work injuries were workers older than 30 years, sleeping 7 hours or less per night, and working 50 hours or more per week. CONCLUSIONS AND OUTLOOK This thesis adds further evidence that sleep problems are a considerable risk for work injuries. We not only systematically confirmed the suggested association between sleep problems and work injuries, we also quantitatively pooled the estimated risks for the first time. Furthermore, this thesis is the first comparison between international and Swiss results. Similar risks for sleep problem related work injuries were observed, and the international findings could therefore be verified for Switzerland. The socioeconomic burden of sleep problem related work injuries was estimated as considerable. Approximately CHF 290 million are spent on the consequences of sleep problem related work injuries in Switzerland every year. Up to every fifth work injury may be prevented if sleep problems are eliminated. The knowledge about the impact of sleep problems on work safety obliges responsible parties to take preventive action. This thesis adds valuable information on how to identify the risk of sleep problem related work injuries. The identification of the work injury types most susceptible to sleep problems may contribute to a better understanding of the injury causation and thus support a comprehensive recognition of injury causes. It may be useful to check workers involved in a fatigue related work incident for the sleep problems that are found to be associated with work injuries in this thesis to prevent them from similar events. Another approach may be to target sleep-related prevention measures to the population most at risk for sleep problem related work injuries identified in this thesis. Future studies on this topic should be conducted in basic research and applied science. Basic research in the field of sleep problem related work injuries needs to better characterise the mechanisms involved in the ways that sleep problems affect work injuries. For this purpose, laboratory simulations and epidemiological studies are needed. Furthermore, newly proposed analysis methods should be verified, and measures to assess which injury relevant aspects of sleep in the workplace setting need improvement. Applied science should be used to provide practical knowledge on how to protect workforces from sleep problem related work injuries. For a successful implementation of fatigue prevention measures, evidence-based information is needed along the causal chain of events potentially leading to an incident. To predict fatigue at the organisational and individual levels, behaviourally based methodologies need post-implementation research to define thresholds. The possibility for reducing the number of work injuries through sleep education needs to be evaluated for targeted injury prevention. Before launching a screening program for sleep problems, questions on feasibility or effectiveness need to be answered. Fatigue detection technologies and fatigue proofing systems need validation. Furthermore, occupational health and safety officers need to be trained in identifying fatigue-related factors that can cause injuries. In practice, many ideas on structural and behavioural strategies for work injury prevention exist. However, there are many unanswered questions about assessing fatigue management in the workplace. These questions need to be resolved before fatigue management systems can realise their full potential for contributing to injury prevention and helping to reduce the number of work injuries

Sleep problems and work injury types : a study of 180 patients in a Swiss emergency department

INTRODUCTION: Sleep problems present a risk for work injuries and are a major occupational health concern worldwide. Knowledge about the influence of sleep problems on work injury patterns is limited. Therefore, the aim of this study was to identify potential associations between different types of work injuries and sleep quality, sleep duration, and daytime sleepiness. METHODS: In this hospital-based study, 180 male and female patients with work injuries were recruited at the Emergency Department of the University Hospital Basel, Switzerland, from December 1st 2009 to June 30th 2011. The data on work injury characteristics, sleep problems, and potential confounders, such as demographic, health, lifestyle, occupational and environmental factors, were collected. Multivariable logistic regression analyses were performed to investigate the relationship between sleep problems and various types of work injury. RESULTS: Each dimension of sleep problems - sleep quality, sleep duration and daytime sleepiness - was a significant risk factor for at least one type of work injury. The strongest association was found for musculoskeletal injuries and falls with short sleep duration (odds ratio [OR] 5.41, 95% confidence interval [CI] 1.81-16.22). The standardised scores of the Pittsburgh sleep quality index (PSQI) and the Epworth sleepiness scale (ESS) did not discriminate between injury types. CONCLUSION: Employees with sleep problems were more likely to suffer from certain types of work injuries. This should be considered by employers monitoring work injuries and implementing prevention measures in the company's health and safety management

Relationship between domain-specific physical activity and different body composition measures in a working population

With respect to the overweight epidemic, this study aimed to investigate the association between domain-specific physical activity and body composition measures in Swiss male employees.; A total of 192 healthy male adults in full-time employment were investigated. Height, weight, and waist circumference were measured and body mass index was calculated. Relative fat mass and relative muscle mass were determined by bioelectric impedance analysis. Physical activity was assessed by the validated International Physical Activity Questionnaire.; In multiple linear regressions, leisure-time activity showed an inverse association with waist circumference and relative fat mass and a positive correlation with relative muscle mass. Work activity was positively related to waist circumference and body mass index.; This study shows that leisure-time activity may be the most effective physical activity domain for body composition. Work activity does not seem to be protective against overweight

Screening for obstructive sleep apnea among hospital outpatients.

BACKGROUND:Obstructive sleep apnea syndrome (OSAS) is common in adults. People with OSAS have a higher risk of experiencing traffic accidents and occupational injuries (OIs). We aimed to clarify the diagnostic performance of a three-channel screening device (ApneaLinkTM) compared with the gold standard of full-night attended polysomnography (PSG) among hospital outpatients not referred for sleep-related symptoms. Furthermore, we aimed to determine whether manual revision of the ApneaLinkTM autoscore enhanced diagnostic performance. METHODS:We investigated 68 patients with OI and 44 without OI recruited from the University Hospital Basel emergency room, using a cross-sectional study design. Participating patients spent one night at home with ApneaLinkTM and within 2 weeks slept for one night at the sleep laboratory. We reanalyzed all ApneaLinkTM data after manual revision. RESULTS:We identified significant correlations between the ApneaLinkTM apnea-hypopnea index (AHI) autoscore and the AHI derived by PSG (r = 0.525; p <0.001) and between the ApneaLinkTM oxygen desaturation index (ODI) autoscore and that derived by PSG (r = 0.722; p <0.001). The ApneaLinkTM autoscore showed a sensitivity and specificity of 82% when comparing AHI ≥5 with the cutoff for AHI and/or ODI ≥15 from PSG. In Bland Altman plots the mean difference between ApneaLinkTM AHI autoscore and PSG was 2.75 with SD ± 8.80 (β = 0.034), and between ApneaLinkTM AHI revised score and PSG -1.50 with SD ± 9.28 (β = 0.060). CONCLUSIONS:The ApneaLinkTM autoscore demonstrated good sensitivity and specificity compared with the gold standard (full-night attended PSG). However, Bland Altman plots revealed substantial fluctuations between PSG and ApneaLinkTM AHI autoscore respectively manually revised score. This spread for the AHI from a clinical perspective is large, and therefore the results have to be interpreted with caution. Furthermore, our findings suggest that there is no clinical benefit in manually revising the ApneaLinkTM autoscore

Sleep problems and work injuries : a systematic review and meta-analysis

OBJECTIVES: Sleep problems are a potential risk factor for work injuries but the extent of the risk is unclear. We conducted a systematic review and meta-analysis to quantify the effect of sleep problems on work injuries.METHODS: A systematic literature search using several databases was performed. Sleep problems of any duration or frequency as well as work injuries of any severity were of interest. The effect estimates of the individual studies were pooled and relative risks (RR) and 95% confidence intervals (CI) were calculated through random effects models. Additionally, the population attributable risk was estimated.RESULTS: In total, 27 observational studies (n = 268,332 participants) that provided 54 relative risk estimates were included. The findings of the meta-analysis suggested that workers with sleep problems had a 1.62 times higher risk of being injured than workers without sleep problems (RR: 1.62, 95% CI: 1.43-1.84). Approximately 13% of work injuries could be attributed to sleep problems.CONCLUSION: This systematic review confirmed the association between sleep problems and work injuries and, for the first time, quantified its magnitude. As sleep problems are of growing concern in the population, these findings are of interest for both sleep researchers and occupational physicians

Obstructive sleep apnea syndrome and sleep disorders in individuals with occupational injuries

Abstract Background Some sleep disorders are known risk factors for occupational injuries (OIs). This study aimed to compare the prevalence of obstructive sleep apnea syndrome (OSAS) in a population of patients with OIs admitted to the emergency room (ER) with hospital outpatients as controls. Methods Seventy-nine patients with OIs and 56 controls were recruited at the University Hospital of Basel, Switzerland between 2009 and 2011. All patients completed a questionnaire and underwent a full-night attended polysomnography (PSG). We considered an apnea–hypopnea index (AHI) > 5 as an abnormal finding suggestive of a diagnosis of OSAS. Results Patients with OIs did not differ from controls regarding sex, age, body mass index, and job risk of OI. Patients with OIs tended to have an abnormal AHI (n = 38 [48%] vs. n = 16 [29%], odds ratio [OR] = 2.32 [95% confidence interval (CI):1.05–5.13]), and a higher AHI (8.0 vs. 5.6 events/h; Cohen’s d 0.28, p = 0.028) compared with controls. Patients with OIs also had abnormal limb movement index, arousal index, and signs of sleep bruxism compared with controls. Compared with 36 controls (66%), 70 patients with OIs (89%) had either excessive daytime sleepiness (EDS), and/or an abnormal finding during PSG (OR = 4.32, 95% CI:1.65–11.52). However, patients with OIs did not differ from controls regarding EDS or oxygen desaturation index. Conclusions Patients treated in the ER for OI had more abnormal findings suggestive of OSAS or other sleep disorders compared with a control group of hospital outpatients. Screening for these conditions should be part of the postaccident medical investigation

Muscle fibre recruitment can respond to the mechanics of the muscle contraction

This study investigates the motor unit recruitment patterns between and within muscles of the triceps surae during cycling on a stationary ergometer at a range of pedal speeds and resistances. Muscle activity was measured from the soleus (SOL), medial gastrocnemius (MG) and lateral gastrocnemius (LG) using surface electromyography (EMG) and quantified using wavelet and principal component analysis. Muscle fascicle strain rates were quantified using ultrasonography, and the muscle–tendon unit lengths were calculated from the segmental kinematics. The EMG intensities showed that the body uses the SOL relatively more for the higher-force, lower-velocity contractions than the MG and LG. The EMG spectra showed a shift to higher frequencies at faster muscle fascicle strain rates for MG: these shifts were independent of the level of muscle activity, the locomotor load and the muscle fascicle strain. These results indicated that a selective recruitment of the faster motor units occurred within the MG muscle in response to the increasing muscle fascicle strain rates. This preferential recruitment of the faster fibres for the faster tasks indicates that in some circumstances motor unit recruitment during locomotion can match the contractile properties of the muscle fibres to the mechanical demands of the contraction

Sleep quality and the risk of work injury : a Swiss case-control study

Sleep problems are a well-known risk factor for work injuries, but less is known about which vulnerable populations are most at risk. The aims of this study were to investigate the association between sleep quality and the risk of work injury and to identify factors that may modify the association. A case-control study including 180 cases and 551 controls was conducted at the University Hospital in Basel, Switzerland, from 1 December 2009 to 30 June 2011. Data on work injuries and sleep quality were collected. Adjusted odds ratios and 95% confidence intervals of the association between sleep quality and work injury were estimated in multivariable logistic regression analyses and were stratified by hypothesized effect modifiers (age, gender, job risk, shift work, sleep duration and working hours). Poor sleep quality was associated significantly with work injury of any type (P > 0.05) and with being caught in particular (P > 0.05). The association between poor sleep quality and work injury was significantly higher for workers older than 30 years (odds ratio 0.01), sleeping 7 h or less per night (odds ratio≤7 1.17 versus odds ratio 0.05) and working 50 h or more per week (odds ratio≥50 1.79 versus odd ratio>50 1.10, P > 0.01). Work injury risk increased with increasing severity of sleep problems (P > 0.05). Prior work injury frequency increased with decreasing sleep quality (P > 0.05). Older age, short sleep duration and long working hours may enhance the risk of work injuries associated with sleep quality