Review Article

Sleep apnea and occupational accidents: Are oral appliances the solution? Abstract Background: Dental practitioners have a key role in the quality of life and prevention of occupational accidents of workers with Obstructive Sleep Apnea Syndrome (OSAS). Aim: The aim of this study was to review the impact of OSAS, the Continuous Positive Airway Pressure (CPAP) therapy, and the evidence regarding the use of oral appliances (OA) on the health and safety of workers. Materials and Methods: Searches were conducted in MEDLINE (PubMed), Lilacs and Sci ELO. Articles published from January 1980 to June 2014 were included. Results: The research retrieved 2188 articles and 99 met the inclusion criteria. An increase in occupational accidents due to reduced vigilance and attention in snorers and patients with OSAS was observed. Such involvements were related to excessive daytime sleepiness and neurocognitive function impairments. The use of OA are less effective when compared with CPAP, but the results related to excessive sleepiness and cognitive performance showed improvements similar to CPAP. Treatments with OA showed greater patient compliance than the CPAP therapy. Conclusion: OSAS is a prevalent disorder among workers, leads to increased risk of occupational accidents, and has a significant impact on the economy. The CPAP therapy reduces the risk of occupational accidents. The OA can improve the work performance; but there is no scientific evidence associating its use with occupational accidents reduction. Future research should focus on determining the cost‑effectiveness of OA as well as its influence and efficacy in preventing occupational accidents. Key words: Continuous positive air pressure, obstructive sleep apnea, occupational accidents, oral appliances, review

INTRODUCTION

conducted among professional drivers. Obtaining data on the frequency of sleep‑disordered breathing, nocturnal sleep disruption, and excessive sleepiness among the working population is an important public health problem.[6,7] It is noteworthy that the identification and treatment of snoring and OSAS in workers can potentially reduce the number of occupational injuries, absenteeism, improve productivity, health, and wellbeing of these professionals.[8‑11]

Maria De Lourdes Rabelo Guimarães, Ana Paula Hermont1 Faculty of Dentistry of the Federal University of Minas Gerais, Belo Horizonte, Brazil, 1 Department of Pediatric Dentistry and Orthodontics, Faculty of Dentistry, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil

Several well‑tolerated and effective treatments for OSAS have demonstrated improvements in the quality of life and reduction in the use of health services and vehicle collisions. [12‑14] Treatments for OSAS can be clinical or surgical, and the clinical treatment options include behavioral measures, and the use of continuous positive airway pressure device (CPAP) or oral appliances (OA).[15]

For correspondence: Dr. Maria de Lourdes Rabelo Guimarães, Faculty of Dentistry, Universidade Federal de Minas Gerais, Belo Horizonte, Rua Benvinda de Carvalho, 105/101, Santo Antônio, Belo Horizonte, Minas Gerais, Brazil, 30330-180. E‑mail: mlourdesrg@ gmail.com

The OA are a noninvasive treatment option for patients with OSAS and it is considered less uncomfortable than CPAP.[16] The American Academy of Sleep Medicine recommends the OA therapy for patients with mild‑to‑moderate OSAS and those with severe OSAS who cannot tolerate CPAP and refuse surgery procedures.[17]

The Obstructive Sleep Apnea Syndrome (OSAS) is characterized by repeated collapse of the upper airway during sleep, resulting in nocturnal hypoxemia and fragmented sleep. Associated brain dysfunctions can be expressed, such as abnormal daytime sleepiness and lack of concentration, and these are common causes of traffic accidents.[1‑4]

The use of CPAP is indicated as firstline treatment for people with high levels of apnea–hypopnea index (AHI) associated with excessive sleepiness [18]; however, there are indications that OA improves subjective sleepiness and sleep‑disordered breathing.[19]

Several studies have associated OSAS with increased risk of traffic accidents[4,5] and the majority of the researches were

Randomized trials assessing the effectiveness of OA found that it

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Access this article online Website: www.ijoem.com DOI: 10.4103/0019-5278.146887 Quick Response Code:

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reduced the excessive daytime sleepiness when compared with patients without treatment.[20‑24] Moreover, when the results of CPAP and OA were compared, there was no significant difference between both therapies.[25‑30] A randomized clinical trial presented improvements on energy and fatigue levels and vigilance and psychomotor speed among patients treated with OA when compared with placebo.[20] Other studies also found improvements in neurocognitive function using the OA, which did not differ statistically from the improvements achieved by the CPAP therapy.[26,27] In 2011, a longitudinal study was conducted with patients with mild‑to‑moderate OSAS who were randomized regarding the treatment for CPAP or OA. The study showed similar improvement from both therapies regarding the AHI and excessive daytime sleepiness; however, the survey sample was not representative.[31] It is worth noticing that changes in the oral appliances design may contribute to different results, once a study comparing devices with different designs showed differences in the improvement of excessive daytime sleepiness.[32] The CPAP treatment significantly reduces the risk of accidents in OSAS patients. [33‑37] Treatment with OA, in addition to being effective to normalize the respiratory disorders, improved work performance of patients with OSAS. [38] However, it still lacks a more comprehensive way to assess the benefit of OA on driving simulation and real driving performance.[14] This article aimed to revise the prevalence and impact of OSA on work performance, occupational impairments, use of health services, and its economic impact. The cost‑effectiveness and effects of the CPAP therapy and especially the role of OA concerning those issues were also investigated.

MATERIALS AND METHODS These were the inclusion criteria used in this article: Articles published from January 1980 to June 2014 concerning patients with a diagnosis of OSA, presenting AHI >5, snorers, upper airway resistance syndrome, age ≥18 years; any study design and the languages were restricted to: English, French, and Portuguese. Exclusion criteria were central sleep apnea, coexisting sleep disorders, regular use of sedatives or narcotics, preexisting lung disease, and psychiatric illness. Searches were conducted on MEDLINE (PubMed), Latin American and Caribbean Literature Data on Health Sciences (LILACS) and Scientific Electronic Library Online (SciELO), in addition to searches from the references of the identified articles. 40

The search strategy was performed by combining the following descriptors: Apnea, snoring, sleepiness, mandibular advancement devices, oral appliances, continuous positive air pressure, cost, economics, cost‑effectiveness, accident, health care utilization, driving, occupational accidents, occupational injury, traffic, commercial vehicle drivers, and work limitation. The analysis was based on critical readings of the articles content. Subsequently, the common contents were identified, grouped, and tabulated to form the thematic analysis and preparation of a critical discourse.

RESULTS AND DISCUSSION During the search, 2188 articles were identified, but 2095 were excluded once they did not meet the inclusion criteria, totaling 99 articles included. Impairments in occupational performance Sleepiness negatively affects cognitive function, therefore it is assumed that patients with OSAS suffer impairments in labor capacity,[9,39‑41] by presenting lack of concentration and attention, memory impairment, and changes in the ability to perform everyday tasks and learning. Moreover, the reduced capacity for executive functions such as completing tasks, can cause loss of motivation and initiative.[9,42] The National Sleep Foundations (NSF) in the United States assessed the sleep of workers and found that those at risk for OSAS had a greater chance of having difficulty when performing cognitive tasks, including problems with concentration and organization and also a greater risk of falling asleep at work, decreased productivity, and absenteeism due to sleepiness.[43] Snoring was also highly associated with excessive sleepiness and work performance impairments.[44] The sleep‑disordered breathing was a common finding among Brazilian professional drivers who presented an OSAS prevalence of 38%. Furthermore, the daytime sleep was fragmented and shorter than nocturnal sleep and more drivers presented extreme sleepiness. It is worth noticing that such deficiencies of sleep can negatively affect performance in driving.[45] Another epidemiological study conducted among Brazilian railroad workers suggested age, body mass index (BMI), and alcohol consumption as associated with an increased risk of developing OSAS and it stressed the need for greater attention to this population, once they are more prone to suffer accidents.[46] In Greece, the prevalence of sleep‑disordered breathing among drivers of rail transport was similar to other studies, but the study reported a low prevalence of drowsy drivers (7.1%). However, this data has to be carefully

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analyzed once it was used a subjective evaluation criterion by Epworth Sleepiness Scale.[47] Among a group of American officers, sleep disorder was identified as an ordinary problem and that it was significantly associated with increased risk of health problems, work performance, and safety outcomes; OSAS was the most prevalent disorder (33.6%). Excessive sleepiness was found in 28.5% of the police officers and there was an increase in the prevalence of physical and mental health disorders, including diabetes, depression, cardiovascular disease, and increased risk of accidents.[48] A study carried out among soldiers identified that 88.2% of the sample were diagnosed with sleep disorders. Insomnia coexisting with OSAS was found in 38.2% of the military and they were significantly more likely to meet criteria for depression compared with control subjects and others with only OSAS.[49] Among young soldiers in Korea, it was found that the prevalence of snoring and high risk of OSAS was 13.5% and 8.1%, respectively. It is worth noticing that this is not a low prevalence considering that the individuals were young and not obese.[50] It was observed that the treatment of OSAS resulted in the reduction of occupational accidents and improved the performance of employees. Therefore, it is advisable to develop strategies for screening effective treatment of OSAS.[51] Nevertheless, it has been difficult to establish the exact effect of untreated OSAS in real driving and traffic accidents. Driving simulators have been used as a cheaper and safer reproducible way to assess the effect of OSAS on different aspects of driving, but despite the benefits provided, the simulator cannot measure all the aspects experienced in a real‑life driving situation.[52] In Canada, useful data from a study of driving in “real life” were evaluated. Over a period of three years patients with mild, moderate, and severe OSAS had an increased rate of traffic accidents when compared with drivers without this condition and had higher rates of road traffic accidents associated with personal injury.[53] Worse performances in driving simulators among subjects with untreated OSAS was also identified by other studies.[54‑56] Nonetheless, after treatment with CPAP, there was an improvement in the driving performance.[36,54,55] It is known that the CPAP therapy improves driving performance and can potentially reduce the risk of accidents, but the benefits provided by CPAP depend on treatment adherence.[57] The results of a study conducted in 2011 suggest persistent impairment in driving simulator during long trips in patients with severe OSAS treated with CPAP. These results support the evidence that some neurobehavioral deficits in patients

with severe OSA are not fully reversed by treatment. More controlled studies with larger samples are needed to confirm these findings and further researches should investigate the causes of residual driving simulator impairment among patients with OSAS treated with CPAP and its association with increased risk of vehicular accident on highway.[57] Test driving simulator was also used to investigate whether OSAS patients had worse labor performance than healthy drivers. The benefits provided by OA and CPAP were also analyzed. The results showed a significantly higher number of lapses in attention among OSAS patients. The total number of lapses of attention was significantly decreased after both therapies, with OA and CPAP, with no significant differences between the two types of treatment.[25] However, a more comprehensive way to assess the benefits of OA on driving simulation tests, and real‑life driving performance are needed to adequately assess its potential role concerning the risk of drowsiness at the wheel represented by OSA.[14] Another important issue that should be discussed concerning the impairments in occupational performance is related to the international driving licensing legislation. A committee established by the European Commission on sleep apnea and driving has been discussing about directives with an approach to patients with moderate or severe sleep apnea, particularly associated with significant sleepiness. Those patients will be prevented from driving, or at least will be prevented from holding a driver’s license, until the condition is successfully treated.[58] The driving licenses may be issued to applicants or drivers with moderate or severe OSAS who show adequate control of their condition and compliance with appropriate treatment and improvement of sleepiness, if any, confirmed by authorized medical opinion. Applicants or drivers with moderate or severe OSAS under treatment shall be subject to a periodic medical review with a view to establish the level of compliance with the treatment, the continued good vigilance, and evaluate the need for continuing the treatment.[58] Occupational injury Many mental functions are reduced in situations of fatigue and sleepiness.[59] It is estimated that 20% of accidents are caused by drivers’ inattention and sleepiness,[60] and the occurrence of drowsiness when driving is a major risk factor for dangerous accidents.[61] Chronic excessive sleepiness and sleep‑disordered breathing were common in a sample of drivers of commercial vehicles in Australia. Sixty percent of drivers had OSAS and 16% had OSAS with excessive daytime sleepiness.[62] Drivers with a high risk for OSAS and a work schedule with little chance of rest

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reported more daytime sleepiness and poor sleep quality in a study conducted among Belgian truckers[63] and Japanese bus drivers.[64] In Brazil, 16% of professional drivers admitted having fallen asleep at the wheel; however, this number increased to 58% when it was reported by colleagues. It was observed that respiratory disorders and snoring are some causes of fragmentation or reduction of rapid eye movement (REM) sleep, which could support the hypothesis that REM sleep deprivation can lead to common complaints such as mental fatigue, irritability, and sleepiness among professional drivers.[65] Nowadays, most European countries have traffic laws directed to sleep‑disordered breathing. [7] The driver screening methods should contain questions about drowsiness at the wheel, habitual snoring, and sleep apneas, as well as the Epworth Index and BMI.[7] After an assuredly effective and efficient treatment, including regular checkups for control and evaluation of symptoms, patients are allowed to drive. Nevertheless, during the interim period between the diagnosis and therapy, drivers can still be considered able to drive, but with limitations (eg, drive short distances and avoid driving on major highways or at night.[7,66] In Brazil, due to the high rate of traffic accidents caused by drowsiness, in 2008, a resolution was approved by the National Traffic Department to reduce the number of accidents caused by drowsiness, fatigue, sleep‑disordered breathing, and changes in biological rhythms.[59] Evaluation of OSA was included in this resolution as well as the requirement of new medical and psychological examinations for all professional drivers.[59] Sleep‑related accidents comprise 16%–23% of all vehicle accidents.[67] Many of these accidents could be prevented by treating sleep‑disordered breathing.[68] However, drivers with symptoms of drowsiness or sleep‑disordered breathing may not report accidents due to concerns of losing their jobs, compromising the results of studies on the association between these disorders and accidents.[62] A study conducted among long distance truck drivers in the United States found that about 20% of drivers presented symptoms of sleep disorders. Drivers who were working with the same company for over a year were more likely to have daytime fatigue, daytime tiredness, restless sleep, hypertension, and increased BMI.[6] Other studies observed a higher prevalence of OSAS in railway workers than in the general population, [46,47] thus necessitating greater attention to this population, due to the greater propensity for accidents. 42

A research conducted with presumably healthy working men also identified a significant association between the complaint of excessive daytime sleepiness and the incidence of sleep apnea.[69] In Turkey, 241 long‑distance drivers were interviewed about symptoms of OSAS, and occupational history. The drivers who had evidence of OSAS underwent polysomnography. Snoring was detected in 56% of all participants and daytime sleepiness was observed in 26.6%. The prevalence of OSAS was 14.1%. There was a significant relationship between the rate of traffic accidents by professionals/year and AHI, lowest saturation, desaturation index, and arousal index. The disease severity was directly proportional to the risk of accidents.[70] Snoring, which is one of the signals present in OSAS, has been associated with increased risk for accidents and morbidity. A study conducted in Hungary found that snoring is common in the adult population. Through interviews, the study showed that especially loud snoring with breathing pauses was strongly associated with health impairment, higher comorbidity, daytime sleepiness, and a higher frequency of accidents.[71] A retrospective evaluation of snoring workers due to suggestive symptoms of OSAS found a significantly higher frequency of occupational accidents among these professionals when compared to the general population of snorers. In this study, all subjects underwent overnight polysomnography in a sleep laboratory and, interestingly, the risk of accidents was high among heavy snorers without apnea and patients with OSAS.[8] A prospective study found that men who reported both snoring and excessive daytime sleepiness were with an increased risk of labor accidents during the 10 years of follow‑up.[72] The high risk of traffic accidents among drowsy drivers was mainly determined by the respiratory effort‑related arousals (RERA) than by the presence of apneas and hypopneas.[73] The RERAs are secondary to upper airway obstructions during sleep and can occur in the absence of apneas and hypopneas, causing excessive daytime sleepiness. Studies using the esophageal pressure measure were performed in habitually sleepy drivers and drivers without this condition. Sleepy drivers with apnea had higher accident rates in five years than drivers in the control group. Nevertheless, a high rate of RERA, but not sleep apnea, was still a risk factor among drivers habitually sleepy. These findings confirm the importance of identifying RERA in routine examinations in sleep laboratories.[73] Just like it occurs with civilians, excessive sleepiness is a risk to the safety of military that operate dangerous

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vehicles, machinery, or carry firearms. Military with untreated OSA are also at risk for suffering from decreased mental alertness and decreased cognitive function due to drowsiness. Military with mild‑to‑moderate OSA and upper airway resistance syndrome (UARS) often have abnormal results in the Maintenance of Wakefulness Test and therefore have a pathological tendency to fall asleep. A study conducted in 2009 among military personnel identified that 32% of the sample had UARS and 68% OSA.[74] Effectiveness and efficacy of CPAP and oral appliances The physician must diagnose sleep apnea and evaluate the patient’s risk for injuries. The patient should be informed about the risks and an appropriate treatment should be instituted. In addition, the doctor should provide a follow‑up plan to determine if the treatment has decreased the patient’s risk for accidents.[75] Although many investigations have pointed out that treatment of primary snoring and OSAS with CPAP or OA contributes to the reduction of vehicle and labor accidents,[12,33,34,36,76] this review did not find any studies evaluating the effectiveness of OA regarding this outcome. Like several other medical treatments, the efficacy of CPAP or OA depends on the degree of identification of OSAS and the degree of adherence to the treatment among the diagnosed individuals. [35] Treatment with CPAP reduces the risk of accidents because it is used by the patient.[77] Nonetheless, adherence to CPAP continues to be a major problem when treating OSAS, although more recent data suggest that adherence may have improved in recent years. However, a recent study found that only 5% of professional drivers diagnosed with OSAS showed adequate adherence to CPAP.[35,78] It is important to include the patients in the treatment decision, offering more than one type of therapy for patients with OSA. Despite the residual apneas with the use of OA, or the highest rate of effectiveness of CPAP in reducing AHI, the similarities between the results of such treatments may be related to the hours of use per night. The OA which are considered to have partial efficacy, when used for prolonged hours may lead to similar outcomes when compared with CPAP.[79] The ability to pre‑select suitable candidates for either treatment is important. Although some predictors of success with OA have been evaluated, further studies are needed to better predict which patient will have a higher level of success with the OA therapy.[79] Less obese patients with mild sleep apnea and certain craniofacial characteristics such as mandibular retrognathia proved to be good candidates for the OA therapy.[80]

When analyzing the economic impact of OSAS, it was highlighted that there was a lack of clarity concerning the epidemiology of accidents in patients correctly treated with CPAP. Furthermore, it was suggested that future studies are needed to evaluate the improvement in the labor activities of OSAS patients before and after treatment, as well as studies evaluating the cost‑effectiveness between surgical and clinical treatments.[10] Most studies regarding the adherence to OA use subjective measures to evaluate the therapy compliance.[81] Nevertheless, a study conducted in 2012 objectively evaluated the use of OA among patients undergoing therapy for OSA by means of a heat‑sensitive microsensor, which was attached to the OA. The overall mean rate of OA use was 6.7 ± 1.3 h per day with a regular users’ rate of 82%. Despite not having a statistically significant difference between the self‑report and the use of microsensor, the safety and feasibility of using this device to objectively measure the OA’s compliance was highlighted.[82] Although, according to a systematic review, many studies have demonstrated the effectiveness of OA in reducing daytime sleepiness and improve the neurocognitive function,[19] the Federal Motor Carrier Safety Administration does not recommend the use of the OA in the treatment of OSAS among professional drivers, once there is no scientific evidence associating the reduction of accidents by using these devices and it is difficult to assess the patients’ treatment adherence.[83] Furthermore, an updated version of the Thoracic Society Clinical Practice Guideline recommended the use of CPAP to reduce accidents, but again the OA were not listed due to lack of scientific evidence about the effects of this therapy on the risk of accidents.[84] The OSAS treatment options may become limited by the conditions of the work environment. The diagnosis of sleep‑disordered breathing may affect the deployable strength of the military personnel due to the difficulty they might face concerning the use of CPAP.[74] Military deployed in desert environment are at a risk of inhaling airborne particulate matter that can harm their health. In this condition, the CPAP therapy can facilitate the inhalation of these particles. Therefore, alternatives to solve this problem such as using foam filters have been tested.[85] Economic impact of OSAS Obstructive sleep apnea affects the daily lives of millions of people around the world and presents a growing economic impact. The evidence linking OSAS with various public health problems such as obesity, diabetes, depression, cardiovascular disease, and accidents has increased.[10] It is estimated that in the United States, the total costs attributable to sleep apnea‑related accidents is quite high. In

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2000, 1400 people died due to vehicular collisions and in 2004 these accidents had a cost of $ 15.9 billion. With regard to the management of accidents, it is estimated that the treatment with CPAP for all drivers who suffer from OSAS would be of $ 3.18 billion. Even taking into account a treatment efficiency of only 70%, there would be a reduction of $ 11.1 billion in collision costs and 980 lives would be saved per year.[13] The literature suggests that treating 500 patients for three years would result in savings more than $ 1,000. 000.[68] A more recent analysis of OSAS’ treatment showed significantly lower costs of the treatment plan. In addition, it was also observed fewer disability claims; cost reduction for disability and fewer lost days of work.[86] A prospective study compared the effects of OSAS between men and women during 1994–2005. An increased risk of absenteeism in subjects with sleep apnea was observed. In women, the major risk was present five years before diagnosis, whereas in men the major risk was observed one year before the diagnosis of OSAS.[87] Education campaigns encouraging members of health plans to seek specific treatment for sleep‑disordered breathing resulted in substantial savings. Two years after the education campaign started, it was computed savings of U.S. $ 4,900.00.[88] Dentists can play an important role in accident prevention through the detection of risk factors by screening their patients for OSAS, evaluating oral/jaws anatomical features, and screening for sleep disorders during the anamnesis.[14] Use of health services and resources Untreated obstructive sleep apnea predisposes patients to various morbidities and consequently increases the use of health services.[10,12,89‑91] The risk assessment of OSAS among workers can help to reduce the national health care burden.[51] Evidence suggests that patients with untreated sleep apnea require a greater amount of health resources. Moreover, adherence to treatment in patients with OSAS results in a significant reduction in hospitalizations and medical applications.[92,93] In 2013 a study comparing the health effects after one month of CPAP and OA therapy identified that despite the CPAP therapy was more effective in reducing the AHI, the therapy with OA had greater adherence, hence both therapies showed similar results.[94] Cost‑effectiveness of OSAS treatment Concerning CPAP therapy, studies in several countries have evaluated its cost‑effectiveness[12,95,96] Some patients have to try more than one treatment option before control of OSAS is reached. Treatment should be individualized 44

and supported by scientific evidence, and the evaluation of cost‑effectiveness is also required. Information about the therapy cost is important for the governments, transport, industry, and insurance agencies to plan actions to decrease the economic impact of untreated OSAS.[97] Data on types of treatment for snoring and OSAS suggested that therapy with OA had lower costs when compared with other treatment modalities.[15] Nonetheless, it has not been evaluated yet the use of OA associated with reduced risk of vehicle and labor accidents. Further studies should evaluate from a social perspective the loss of work productivity, increased absenteeism, insurance, and costs and assess the use of OA in preventing occupational accidents.[10] The cost‑effectiveness of CPAP was compared with the OA therapy and lifestyle advice using a method of quality‑adjusted life year (QALY) in a life perspective. On average, CPAP was associated with higher costs than other therapies. However, in another analysis CPAP was more profitable than OA. Therefore, regarding adults who suffer from moderate or severe symptomatic OSA it was concluded that CPAP has better cost‑effectiveness when compared with OA and lifestyle advice.[98] The OA are now widely prescribed for the treatment of OSAS, either as a primary or as an alternative measure to those patients unwilling or unable to tolerate CPAP therapy. Although CPAP has been shown to be more effective than OA [19] and highly cost‑effective, [36] there are increasing evidences that OA improve drowsiness, blood pressure, and indices of sleep‑disordered breathing.[79] Moreover, many patients who respond to both treatments generally prefer to use OA.[16] Despite the limited evidence on the cost‑effectiveness of OA, through this literature review it can be observed that OA are economically less attractive than CPAP, but remain as a cost‑effective treatment for patients who do not want or do not adhere to treatment with CPAP.[99]

CONCLUSION This review highlights the fact that OSA is a prevalent disorder among works, leads to increased risk of occupational accidents, greater use of health services, and has a significant impact on the economy. The CPAP therapy reduces the risk of occupational accidents. Furthermore, it has been shown to be cost‑effective, improve the work performance, and reduce health burdens. Regarding OA, despite showing an improvement in work performance, there is no scientific evidence of occupational accidents reduction. Moreover, there is limited evidence of

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its cost‑effectiveness and its effect on reducing the use of health services. Due to the lack of evidence regarding the use of OA for occupational accidents, future research should focus on determining the cost‑effectiveness, influence, and efficacy of these devices in preventing occupational accidents among workers who suffer from OSA.

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