Original contributionScreening for obstructive sleep apnea: an evidence-based analysis
Introduction
Sleep is a basic human need in which there is a transient state of altered consciousness with perceptual disengagement from one's environment. The average human spends 6 to 8 hours per day (about one third of his or her lifetime) sleeping. Contrary to common perception, sleep is an active process involving complex interactions between cortical, brainstem diencephalic, and forebrain structures. There is significant metabolism and oxygen consumption during this state of “rest,” and any disruption of oxygenation or interruption of this physiological process can lead to manifestations such as snoring, choking sensations, apneic episodes, poor concentration, memory loss, or daytime somnolence.
Snoring is caused by the vibration of the structures in the oral cavity and oropharynx—the soft palate, uvula, tonsils, base of tongue, epiglottis, and pharyngeal walls. It has historically been considered a nuisance and an objectionable social problem. However, snoring is important because it may represent an alarm to alert one to the possibility of a sleep disorder. Sleep disordered breathing (SDB) is a spectrum of diseases that includes snoring, upper airway resistance syndrome, and obstructive sleep apnea (OSA). Obstructive sleep apnea is a common sleep disorder. Young et al [1] studied 602 state employees with a formal overnight polysomnography and found that the incidence of SDB was 24% in men and 9% in women. Most of these patients are undiagnosed. It is estimated that up to 93% of women and 82% of men with moderate to severe OSA remain undiagnosed [2].
It is well documented that SDB has profound effects on the cardiovascular and respiratory systems and on neurocognitive function. The Sleep Heart Health Study and the Wisconsin Sleep Cohort [3], [4] have demonstrated a strong link between SDB and hypertension. This is believed to be due to sleep fragmentation, intermittent hypoxemia, and increased sympathetic tone [5]. This increased sympathetic tone is manifested not only during the nocturnal hypoxic events, but also during the day as systemic hypertension. There is convincing evidence of the association between SDB and cardiovascular disease [6]. The physiologic changes that are the result of recurrent apneas and hypoxemia can cause acute thrombotic events [7], [8], atherosclerosis [9], [10], and cerebrovascular accidents. There is a higher mortality rate among patients with cardiovascular disease who also have SDB [11], [12]. Sleep-disordered breathing has also been associated with an increased risk of congestive heart failure [13], and treatment can improve heart failure symptoms. An essential public health priority is the diagnosis of all patients with OSA to prevent development of severe cardiovascular morbidity and mortality.
The gold standard for diagnosing OSA remains the attended overnight level I polysomnogram. However, these studies suffer from limited resources, including recording beds, high cost, long waiting lists, and intense labor requirements. Moreover, elderly or sick patients often find the polysomnography (PSG) equipment too cumbersome, and may be reluctant to spend the night in the sleep laboratory. Several authors have therefore investigated the application of clinical predictors or questionnaires that may help identify higher-risk patients. Single and multiple channel monitoring systems have been evaluated for the ability to screen for OSA. The reliability and accuracy of these screening tools are largely unproven, however, and it is unclear if they are capable of predicting the severity of OSA. These issues are explored in this current analysis.
Section snippets
Clinical predictive models
Symptoms of OSA include snoring, choking at night, witnessed apneic episodes, nocturia, and frequent arousals. Daytime manifestations are excessive daytime somnolence, poor concentration, poor memory, mood changes, and irritability. Puvanendran and Goh [14] studied 220 snorers who underwent an attended, hospital-based overnight polysomnogram and found that 87% of these habitual snorers have OSA. Tami et al [15] studied 94 habitual snorers and found an even lower incidence of only 72% of snorers
Screening devices
Several screening devices designed to assess the severity of OSA have emerged. They evaluate one or more parameters, and most are still undergoing validation. These devices serve to aid the physician in decision-making and should be used with prudence.
The ideal screening device for OSA should be cheap, easily accessible, easily used with the minimal instructions, have no risk or side effects to the patient, and be safe and accurate. It should be capable of being issued by relatively unskilled
Conclusion
Obstructive sleep apnea is common, and most patients remain undiagnosed. These patients have a higher risk of hypertension and other cardiovascular morbidities if left untreated. Because the gold standard for the diagnosis of OSA (level 1 polysomnography), is cumbersome, expensive, labor-intensive, and requires expertise, it is desirable to explore clinical predictive models, questionnaires, and simple screening devices. Although there are several promising models and screening devices
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