ABSTRACT
Obstructive sleep apnea (OSA) is a disorder that commonly affects middle-aged women and men in the United States (1). The prevalence of OSA reported in the literature has a wide range owing to inconsistencies in the definition and sampling biases. On the basis of pooled data from four large prevalence studies that used similar in-laboratory monitoring, diagnostic criteria, and sampling methods, it is estimated that one in five white adults with a body mass index (BMI) of 25-28 kg/m2 have an apnea-hypopnea index (AHI) ≥ 5 to < 15 (mild disease) and 1 in 15 have an AHI ≥ 15 (moderate to severe disease) (1-5). This classification of disease severity is often used, though it has little validity. It is known that long apneas or hypopneas may lead to important drops in oxygen saturation (SaO2), and at the same time owing to their duration, to a lower number of events per time unit. An alternative proposed method is to use a combined number of events per unit time and level of SaO2 drops as criteria for severity, but even this approach may not be solid, as neurocognitive function and alertness may be affected even with snoring and shorter duration of hypopneas than with long obstructive apneas; “severity” is thus also based on these variables that are normally used to define “impairment.”
