Identifying Patients With Sleep Apnea

Abstract

Over the past decade, our knowledge of the healthrelated consequences of obstructive sleep apnea syndrome (OSAS) has increased substantially. Obstructive sleep apnea is a common medical condition characterized by recurrent episodes of breathing cessation during sleep associated with collapse of the upper airway. Such apneas may be associated with oxygen desaturation and often are terminated by brief arousal from sleep. One of the first major reports describing the possible adverse consequences of sleep apnea came from the Henry Ford Hospital in 1988. A significant increase in mortality was reported during an 8-year period in patients with severe OSAS compared with those with less severe OSAS. This increase in mortality was mitigated by both tracheostomy (up to that time the most accepted treatment of severe OSAS) and continuous positive airway pressure (CPAP). Subsequently, several more studies corroborated this finding of increased mortality associated with OSAS. What is the cause of this increase? Several studies have revealed a 2 to 3 times greater incidence of automobile crashes related to excessive daytime sleepiness in many patients with OSAS. Performance in driving simulators is impaired in patients with OSAS but improves when the patients are treated with CPAP. Also, OSAS is associated with an increased risk of numerous cardiovascular diseases. For example, OSAS has been associated with an increased prevalence of arterial hypertension both in animal studies and in large epidemiological studies such as the Wisconsin Sleep Cohort Study and the National Institutes of Health–sponsored Sleep Heart Health Study. Furthermore, OSAS is associated with an increased prevalence of coronary artery disease and stroke. One remarkable finding in these studies is that even mild OSAS is associated with an increased prevalence of cardiovascular diseases. Sleep-disordered breathing is common in patients with congestive heart failure. Treatment of OSAS in patients with congestive heart failure has improved survival rates and left ventricular ejection fractions. Together, these findings clearly show that OSAS is a serious condition with major health-related consequences and that identification of patients with OSAS is important. In 1993, the Wisconsin Sleep Cohort Study reported that in individuals aged 30 to 65 years, the prevalence of sleep-disordered breathing could be as high as 9% in women and 24% in men (although the calculated prevalence depended on the definition used). Prevalence rates may be higher in the elderly population. However, because of the increase in the epidemic of obesity in the US population, undoubtedly these estimates of the prevalence of OSAS have increased accordingly. Recent data show that sleep-disordered breathing may be common in children as well, especially in children who are overweight, have large tonsils, snore loudly, or have craniofacial abnormalities. Children with sleep-disordered breathing may experience impaired cognitive function and impaired school performance. The gold standard in the diagnosis of OSAS is facilitybased polysomnography. Polysomnography is used to monitor electroencephalographic activity, muscle activity, and various cardiorespiratory parameters including airflow, respiratory effort, oximetry, and electrocardiographic activity. A trained polysomnographic technician monitors the patient in real time, makes adjustments for faulty signals, and analyzes and scores the data. The studies are interpreted by sleep specialists. However, in many communities, the number of beds is insufficient to accommodate the demand for sleep studies. As a result, there is often a delay between the time a primary care physician initially suspects the diagnosis and the time that OSAS is diagnosed and treated with CPAP. Hence, there have been efforts to