Disorders of glucose metabolism in sleep apnea

Sleep is a complex behavioral state that occupies one-third of the human life span. Although viewed as a passive condition, sleep is a highly active and dynamic process. The sleep-related decrease in muscle tone is associated with an increase in resistance to airflow through the upper airway. Partial or complete collapse of the airway during sleep can lead to the occurrence of apneas and hypopneas during sleep that define the syndrome of sleep apnea. Sleep apnea has become pervasive in Western society, affecting similar to 5% of adults in industrialized countries. Given the pandemic of obesity, the prevalence of Type 2 diabetes mellitus and metabolic syndrome has also increased dramatically over the last decade. Although the role of sleep apnea in cardiovascular disease is uncertain, there is a growing body of literature that implicates sleep apnea in the pathogenesis of altered glucose metabolism. Intermittent hypoxemia and sleep fragmentation in sleep apnea can trigger a cascade of pathophysiological events, including autonomic activation, alterations in neuroendocrine function, and release of potent proinflammatory mediators such as tumor necrosis factor-alpha and interleukin-6. Epidemiologic and experimental evidence linking sleep apnea and disorders of glucose metabolism is reviewed and discussed here. Although the cause-and-effect relationship remains to be determined, the available data suggest that sleep apnea is independently associated with altered glucose metabolism and may predispose to the eventual development of Type 2 diabetes mellitus.