Screening for Sleep-Disordered Breathing at Workplaces

Industrial Health 2005, 43, 53 57 Review Article Screening for Sleep-Disordered Breathing at Workplaces Takeshi TANIGAWA 1 *, Seichi HORIE 2, Susumu SAKURAI 1 and Hiroyasu ISO 1 1 Department of Public Health Medicine, Doctoral Program in Social and Environmental Medicine, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Japan 2 Department of Health Policy and Management, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan Received October 3, 2004 and accepted November 16, 2004 Abstract: Sleep-disordered breathing (SDB) is a condition of repetitive episodes of decreased or arrested respiratory airflow during sleep. Many workers over the world remain undiagnosed and untreated for SDB, and leaving themselves at the high risk for accidents and cardiovascular disease. Since, the Japanese Ministry of Land, Infrastructure and Transport distributed the sleep apnea syndrome manual together with sending an official notice to relevant bodies in all over Japan in March, 2003, employees and employers are expected to co-operate to prevent SDB-related accidents at work. We have conducted several surveys using the pulse-oximetry to detect SDB in working populations and found the high prevalence of SDB among workers in Japan, as many as in the US and EU countries. The proper use of the result from the screening for SDB seems to be beneficial both to workers and employers by maintaining occupational safety and by preventing future development of cardiovascular disease. Key words: Sleep-disordered breathing, Occupational health, Pulse-oximeter, Blood pressure, Screening Introduction In this review, we are focusing on the following subjects to address various issues of screening for sleep disordered breathing (SDB) at workplaces: 1) SDB and occupational accidents, 2) SDB and Health, 3) How to carry out a screening for SDB at workplace, 4) Epidemiological evidence on SDB estimated by pulse-oximetry, 5) Importance of screening for SDB from social aspect, 6) Health Promotion and SDB, 7) SDB and the insurance company, 8) Responsibility of employees, employers and the government for SDB related *To whom correspondence should be addressed. Sponsorship: This study was supported in part by grants from the Japanese Ministry of Education, culture, Sports, Science and Technology (Grantin-Aid for research B: 14370132). occupational accidents, 9) Importance of medical network for final diagnosis and treatment of SDB. SDB and Occupational Accidents Sleep-disordered breathing (SDB) is a condition of repetitive episodes of decreased or arrested respiratory airflow during sleep 1). SDB raises the risk of automobile accidents and occupational accidents due to excessive daytime sleepiness and a lack of attention 2 4). These accidents during work time lead to the reduction of productivity as well as impairment of health. Thus, the prevention of accidents due to SDB should be conducted through occupational health activities. On February 26, 2003, a Shinkansen (the bullet train) stopped by automatic train control system at Okayama

54 T TANIGAWA et al. station after the driver took 8-min doze while the train ran at 270 km/h. The driver was diagnosed as severe sleep apnea syndrome (SAS). The Japanese government then found that there had been no measure for detecting SAS/SDB for professional drivers, crews or pilots. SDB and Health As for a health problem, SDB has found to be associated with hypertension. Recently, several population-based studies with large sample sizes have demonstrated a positive association between SDB measured by polysomnography (PSG) and blood pressure levels/hypertension, independent of age, obesity and other confounding variables 5 8). Moreover, the causal relationship between SDB and hypertension has been supported by both epidemiological and animal experimental studies. The relative risk of incident hypertension was 2.89 (95% CI, 1.46 5.64) among subjects with apnea-hypopnea index (AHI) 15 compared with subjects with AHI = 0 by a 4-yr follow-up of the Wisconsin Sleep Cohort 9). An animal experiment using a canine model demonstrated that daytime blood pressure increased after experimentally induced intermittent airway occlusion during sleep and fell after a nighttime sleep with quiet breathing 10). The erectile dysfunction has also been reported to be associated with SDB, and this association was thought to be caused by a nerve dysfunction due to nocturnal hypoxia 11 13). How to Carry out a Screening for SDB at Workplace When we conduct SDB screening at workplaces, we will have various delicate problems, such as a guarantee of working condition, maintenance of work safety, privacy protection, a prognosis and rearrangement as well as reinstatement of workers with SDB. To overcome these complicated situations, role of occupational physicians to pursue adaptation of work to the workers and thorough understanding of SDB screening by employees seems to be important. Screening for SDB by questionnaire At the annual health check-up in the workplace, we can use a questionnaire of screening for SDB including snoring, excessive daytime sleepiness, witness of stopped breathing during sleep and perceived insufficient sleep at the morning. Questionnaire on sleepiness Epworth Sleepiness Scale (ESS) 14) is a questionnaire on sleepiness often used in clinical and epidemiological studies. For reasons with a high score of the ESS, we ask them whether they are short of sleep due to their lifestyles such as hard work and waking up late at night. If they have no such lifestyles, we then need to make further examinations for sleep disorders. However, sleep disorders can not be negated for persons with a low score of ESS due to the following reasons: 1) some patients with severe SDB perceive no sleepiness due to frequent short nap, 2) chronic sleepiness diminishes perception of sleepiness, which is supported by a chronic sleep-restriction experiment maintained 4 h or 6 h of nocturnal sleep for 14 consecutive days; a subjective sleepiness score rose steeply in the first 3 d in both groups having 4 h and 6 h nocturnal sleep but the profiles were near-saturating on subsequent days in both two groups 15), 3) there may be considerable inter-individual variation in susceptibility to sleepiness resulting from SDB 16) and 4) intentional underreporting of sleepiness by workers to avoid a possible disadvantageous action by the employers. Questionnaire on aggravating factors for SDB Nasal obstruction and discharge, smoking status, and alcohol intake are important factors to aggravate SDB. An increased amount of smoking and/or beverage including caffeine (coffee, tea, cola, green tea) may also be a marker for assessing an extent of sleepiness. Screening for SDB using the pulse-oximetry The pulse-oximetry is a good measure for SDB screening in workplace. The polysomnography is the gold standard for monitoring nocturnal sleep in clinical setting. However, for early detection and treatment of severe SDB in general population i.e., worksites and communities, polysomnography is not a practical approach to screening for SDB. The pulse-oximetry is available not only for sleep specialists but also for general physicians, occupational physicians and public health nurses. PULSOX-3Si (Minolta Co., Osaka, Japan) is a pulseoximetry attached for one night of sleep at home. The internal memory of this device stores the values of blood oxygen saturation by performing a moving average for the last 5 seconds, updated every second; this sampling time is short enough to avoid underestimation of oxygen desaturation 17). Data is to be downloaded to a personal computer via an interface (PULSOX IF-3; Minolta) and analyzed using a software supplied with the equipment (DS-3 ver. 2.0a; Minolta). We use the value of oxygen desaturation per hour (oxygen desaturation index, ODI) as an indicator of SDB. A 3% ODI is as an index of oxygen desaturation, representing Industrial Health 2005, 43, 53 57

SCREENING FOR SLEEP-DISORDERED BREATHING 55 Fig. 1. The pattern of oxygen desaturation and pulse rate in a normal subject (left) and a patient with severe sleep disordered breathing (right). the number of events per hour of recording time in which blood oxygen fell by 3%. Since the duration of sleep estimated by pulse oximetry is often longer than the true total sleep time, we use a sleep log in order to exclude the waking time from the analysis and thereby minimize potential overestimation of the sleep duration. Generally, the criteria for SDB is defined by 3% ODI level as 5 and 15 events per hour, corresponding to mild and moderate-to-severe SDB, respectively. The validity of the pulse oximetry was confirmed by synchronous overnight recording of both PULSOX-3Si and standard polysomnography (PSG) among 256 consecutive patients (mean BMI, 26.8 kg/m 2 ) who had been referred to a sleep-disordered breathing center: sensitivity of 80% and specificity 95% for detecting an apneahypopnea index (AHI) 5 using a cut-off threshold ODI = 5, and sensitivity of 85% and specificity 100% for detecting an AHI 20 using a cut-off threshold ODI = 15 18). The evaluation of SDB during sleep at home has the advantage of providing a more realistic estimation of prevalence and severity of SDB compared with hospital/ laboratory studies due to the maintenance of regular daily habits of sleep, physical activity, diet and ethanol intake in general population. Thus, the use of pulse-oximetry would be a practical approach to screening for SDB out of so many undiagnosed workers in Japan. Figure 1 shows two examples of data by the home pulseoximetry. The data on the left side shows a normal pattern of oxygen saturation and pulse rate during a whole sleep. The data on the right side shows a typical pattern of severe SDB. He was 64 years old, and he was suffering from excessive sleepiness in recent 10 yr and he sometimes overran the centerline during his driving to work because of a doze. However, he had no idea for his sleepiness until he took the screening for SDB. He took medication for hypertension for more than 30 yr. His score of the ESS was 18/24, which showed an excessive daytime sleepiness. He was referred to the sleep specialist and treated by the continuous positive airway pressure (CPAP). His excessive sleepiness disappeared and his blood pressure became stable after the treatment. The CPAP therapy is admitted for the Japanese medical insurance system on condition that patients with SDB are diagnosed as having AHI level 20 per hour of sleep time. According to our epidemiological surveys using home pulseoximetry, 9% of apparently healthy male subjects aged 40 to 69 years old having 3% ODI level of 15 19), which corresponded to having an AHI of 20. This evaluated prevalence of SDB in Japanese population is high as in the US and EU countries 16). Epidemiological Evidence on SDB Estimated by Pulse-oximetry To examine the relationship between SDB and blood pressure levels among Japanese men, we conducted a population-based cross-sectional study of 1,424 men aged 40 69 yr in rural and urban communities. The 3% ODI level was positively associated with systolic and diastolic blood pressure levels; a 5 event per hour increment of the 3% ODI level was associated with 0.8 mmhg (95%

56 T TANIGAWA et al. confidence interval [CI], 0.0 1.6) greater systolic blood pressure and 0.7 mmhg (95% CI, 0.3 1.1) greater diastolic blood pressure after adjustment for confounding variables. The multivariate odds ratio of hypertension for the low (3%ODI<5) versus high (3%ODI>=15) category of 3% ODI level was 1.63 (95% CI, 1.1 2.5). This association was more evident among overweight than non-overweight individuals 20). We also found a significant positive association between usual alcohol consumption and the severity of SDB among middle-aged Japanese men, independent of age, BMI and smoking. The relationship was more evident among men with lower BMI than among men with higher BMI. This finding emphasizes the importance of alcohol abstinence in non-overweight men with SDB 19). Importance of Screening for SDB from Social Aspect Workers with SDB who have excessive sleepiness often take naps at work, even at important business meeting or driving. Some of them have irritation, tendency to get angry and fatigue caused by impairment of quality of nocturnal sleep. It is difficult for their colleagues and supervisors to distinguish these symptoms from their personality. Thus, workers with SDB tend to have conflicts with colleagues at work, and have evaluated less evaluation from supervisors. Furthermore, snoring could be a psychological stressor for their bed partners. Therefore, the early detection of SDB by screening in workplace must be of importance to reduce these social disadvantages of workers with SDB. Health Promotion and SDB Control of overweight, modification of alcohol consumption, smoking cessation, and to avoid medication use impairing the central nervous system is important to improve a condition of SDB. These general activities of health promotion, which can be performed as occupational health programs, may promote adaptation of the worker with SDB. SDB and the Insurance Company To date, most of the life and property insurance companies in Japan have no clear policy for the acceptance/rejection criteria for contracting life and car insurance in clients with SDB. It is afraid that, insurance companies might reject or require extra charge for their clients who was diagnosed as SAS and treated by CPAP. SDB patients treated by CPAP are considered to restore daytime wakefulness and reduce cardiovascular risk. Therefore, they must be treated equally without discrimination, otherwise, those who have daytime sleepiness and/or snoring would not consult to sleep physicians for diagnosis of their SDB. These situations will increase the number of undiagnosed SDB patients and raise the total risk of accidents in our society. Responsibility of Employees, Employers and the Government for SDB Related Occupational Accidents Industrial Safety and Health Law in Japan requires employers to provide their employees with the annual health check-up including blood pressure measurement, ECG, blood chemistry examinations. The legislations for passenger car (or motor truck) transportation industry prohibit the drivers to drive when they have illness, fatigue, alcohol intake, and any other reasons that may disturb a safety driving. However, until the Shinkansen accident on February 26, 2003, there had been no exact measurement were officially recommended to protect the passengers or drivers from the excessive sleepiness at driving due to sleep apnea syndrome (SAS). To enlighten the transportation industry, the Ministry of Land, Infrastructure and Transport distributed the SAS manual together with sending an official notice to relevant bodies in all over Japan in March, 2003 (http://www.mlit.go.jp/kisha/ kisha03/09/090318/090318.pdf). The major targets of the SAS manual are commercial drivers and their employers who would be expected to learn the minimum knowledge of pathophysiology, screening, diagnosis and treatment for SAS. This manual emphasizes that the employers should not take any disadvantageous actions against the employees when they are diagnosed as SAS. Importance of Medical Network for Final Diagnosis and Treatment of SDB Most of the corporate health services at workplace in Japan do not conduct PSG or perform the CPAP therapy. Thus, occupational physicians who detect untreated SDB patients by screening should make a referral to clinics or hospitals in their communities where further sleep studies such as PSG are available. Since medical resources for conducting PSG in Japan, at the present, is insufficient for the estimated number of untreated patients with SDB, the enhancement of medical network for final diagnosis and treatment of SDB is essential to control SDB at workplaces. Industrial Health 2005, 43, 53 57

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