Obstructive sleep apnea: diagnosis, epidemiology, and economics

Obstructive sleep apnea (OSA) is a disorder characterized by intermittent upper-airway collapse, which impairs ventilation and disrupts sleep. Factors that contribute to upper-airway collapse include reduced upper-airway dilator muscle activity during sleep, specific upper-airway anatomical features, decreased end-expiratory lung volume, ventilatory control instability, sleep-state instability, and rostral fluid shifts in the recumbent position. The relative contributions of these factors vary between individuals with OSA, and this may have implications as to which treatments are efficacious for an individual. OSA is common in adults; males, older individuals, and the obese are at higher risk. There is uncertainty in how to measure severity of sleep-disordered breathing, what cut-off to use to demarcate abnormal, and how to define the clinical syndrome. Identifying patients at higher risk who should have a sleep study is relatively simple, involving assessment of several factors, such as snoring, witnessed apnea/self-reported gasping, hypertension, body mass index, and neck circumference. As would be expected from a disorder that causes morbidity, OSA is associated with substantial economic costs to society, including increased medical costs. A reduction in medical costs in a diverse adult patient population with OSA after therapy has not been convincingly demonstrated. Nevertheless, the results of cost-effectiveness analyses strongly support the cost-effectiveness of continuous positive airway pressure therapy in patients with moderate to severe OSA, relative to other standard medical therapies that society is willing to pay for.