Update on Obstructive Sleep Apnea and Its Associated Metabolic Abnormalities: Insulin Resistance, Metabolic Syndrome, and Type 2 Diabetes Mellitus

Obstructive sleep apnea is characterized by repeated episodes of upper airway collapse during sleep, leading to apneic and hypopneic episodes, oxygen desaturation, and sleep fragmentation. This condition is closely associated with features of "metabolic syndrome" as well as overt diabetes. Although the association of metabolic abnormalities clearly portend increased cardiovascular risk, it remains unclear to what extent obesity confounds these associations. Attempts to demonstrate a causal relationship between obstructive sleep apnea and insulin resistance have yielded conflicting results. Although several recent studies have demonstrated a relationship between obstructive sleep apnea and diabetes mellitus independent of obesity, there are currently limited data demonstrating a strong causative link. The currently proposed pathophysiology involves intermittent hypoxia, sleep fragmentation, sympathetic activation, oxidative stress, an increase in proinflammatory adipocytokines, and hyperleptinemia and leptin resistance. Although continuous positive airway pressure has shown promise in treating obstructive sleep apnea and its associated metabolic derangements, two recent large, randomized controlled trials have redoubled the emphasis on weight loss in treating the triad of metabolic syndrome, diabetes, and obstructive sleep apnea. Weight loss and aggressive lifestyle intervention remain a common treatment modality for all of these conditions and should always be considered first-line treatment for this clinical construct.