National Commission on Sleep Disorders

¶ … National Commission on Sleep Disorders Research reports that approximately 12 to 18 million middle-aged Americans have obstructive sleep apnea (OSA), comparable in prevalence to the levels of asthma or diabetes, and that OSA is a likely cause of about 38,000 cardiovascular deaths annually. Those afflicted with OSA are also at greater risk for metabolic and cardiovascular disorders such as diabetes, hypertension, arrhythmias, and coronary artery disease. Despite being a common disorder, OSA remains overlooked by many primary care providers. Polysomnography is the definitive diagnostic test, which provides objective documentation of apnea and hypopnea.

As cited in Brogram, Files and Zeigler, (2010), mild forms of OSA affect one in five American adults and moderate to severe forms, one in fifteen, not including elderly or children. Of these, as many as 90% of those affected are not presently diagnosed.

Recently, due to the common comorbidity with cardiovascular disease, the healthcare community has been placing a greater emphasis on OSA, yet still many physicians do not recognize the importance of sleep for general well being and are not knowledgeable about the biochemical conditions or risk factors of interrupted sleeping patterns. Patients are not routinely asked about the quantity and quality of their sleep.

Conducting a thorough examination and obtaining a detailed history of sleeping habits help form a basic clinical impression of a person's possible OSA, but a polysomnography in a clinic or lab is required to confirm the diagnosis. The term polysomnography is derived from the Greek "poly" or many, "somno" or sleep, and "graphy" or to write, and refers to a number of overnight tests performed on patients to evaluate sleep disorders.

It normally consists of analyzing a person's oral and nasal airflow, blood pressure and oxygen level, electrocardiographic activity, brain wave pattern, and movement of the eyes, respiratory muscle and limbs. Overnight polysomnography is the only diagnostic modality recommended by the American Academy of Sleep Medicine. Overnight pulse oximetry and home sleep studies are helpful in ruling out OSA, but are not recommended for diagnosis.

Polysomnography helps diagnose and evaluate sleep apnea, a common disorder in middle-aged and elderly obese men where the muscles of the soft palate in the back of the throat relax and close the airway during sleep. This may cause loud snoring and gasping for air at night an excessive sleepiness during the day. The results are expressed using the number of apneic and hypoapneic (AHI), episodes that a patient experiences each sleeping hour. Apnea is defined as airflow cessation lasting for ten or more seconds.

The definition of hypopnea has varied over time. The Clinical Practice Review Committee of the American Academy of Sleep Medicine and the Centers for Medicare & Medicaid Services define hypopnea as airflow reduction of at least 30% lasting for at least ten seconds and resulting in 4% or more oxygen desaturation. Some laboratories also require an associated arousal (Mendez & Olson, 2006). Narcolepsy, when people have sudden attacks of sleep and/or cataplexy, sleep paralysis or hallucinations at sleep onset, is also diagnosed through polysomnography.

Parasomnias, including sleep walking, talking in one's sleep, nightmares, and bedwetting and seizures during sleep are also evaluated by with polysomnography. A concern of polysomography is the "first night" effect, which may present inaccurate results due to the patient's lack of or unfit sleep from electrode discomfort.

Gouveris and colleagues (2009) conducted a study to test the difference between the polysomnographic values of the AHI, minimal oxygen saturation (SpO2), oxygen desaturation index (ODI) and arousal index that were recorded on two successive nights in 130 people, 23 to 80 years of age, with sleep-disordered breathing (SDB) and associated upper airway pathology. AHI, minimal SpO2, ODI and arousal index values of the first night were compared to those of the second night using Wilcoxon signed-rank test.

Although there were no significant statistical differences between AHI, SpO2, ODI and arousal index values between the two nights, 15% of the patients showed significant variability in the AHI between the two recordings. Further, in 6% of the patients, a diagnosis of severe OSA would have been missed by conducting only one night of the sleep study. Normally, it is enough to have one night of sleep study to clearly diagnosis severe OSA in patients with sleep-disordered breathing and upper airway pathology.

However, the others suffering from the severe OSA would not have been found and many with AHI variability would have been missed. Ahmadi et al. (2009) wanted to investigate AHI on two nights due to a concern with variability of the disorder and impact on clinical diagnosis. They conducted polysomnographies with 193 sleep clinic patients over two consecutive nights to analyze AHI variability.

Anonymized records from five individuals with significant night-to-night AHI variability participated: the two-night tests from two patients were represented as four individual polysomnographies; the two-night tests for two others were represented as being obtained from two different sleep clinics; the last patient's results were shown as a two-night study.

Twenty-two sleep experts at the Associated Professional Sleep Societies meeting diagnosed the results after being told that tests were from seven patients: four with single-night and two with two polysomnographies, each one from a different clinic; and one patient with a two-night test. The results showed that 21% of the patients had a nightly AHI variability of more than 5. Forty-eight percent of everyone tested had a significantly higher AHI on the first night, and 41% had a significantly higher AHI on the second night.

Sleep apnea due to low AHI would have been undetected in 20% of the people on one night. In addition, 13% of all patients had a more severe sleep apnea classification based on the second night of polysomnographies. In regard to the seven cases, 27% to 36% of sleep experts did not accurately identify sleep apnea especially when presented with the polysomnographies containing the lower AHI. Frequency of missed sleep apnea diagnoses were reduced to 15% to 18% when information from two tests were presented to the sleep professionals.

This study reinforces the variability that exists from one night to the next in polysomnography respiratory testing. In addition, identification of sleep apnea in some individuals is reduced when sleep experts are provided with only one recording result. The clinical implication is that approximately13% of sleep clinic patients may benefit from a second night of testing. As noted previously, at-home testing normally have to be confirmed. Levendowski et al. (2009) tested the variability of AHI obtained in home at four- to six-month intervals and through polysomnography.

When comparing the test-retest AHI and AI, the.