Sleep-disordered breathing, glucose intolerance, and insulin resistance.

Sleep-disordered breathing (SDB) is a common condition with prevalence estimates of 2-4% in the general population. Epidemiological data suggest that SDB is an independent risk factor for cardiovascular disease. Glucose intolerance and insulin resistance are also well-recognized risk factors for the development of cardiovascular disease. A number of recent clinic-based studies suggest that, independent of obesity, SDB may adversely affect glucose tolerance and insulin sensitivity. The purpose of this study was to systematically review the evidence for the link between SDB, glucose intolerance, and insulin resistance. A MEDLINE search for SDB and metabolic disorders was performed and 24 articles that met the inclusion criteria were identified. Population-based studies indicate that habitual snoring is independently associated with glucose intolerance and insulin resistance. Studies that have used objective measures of SDB (e.g. polysomnography) provide further support for an independent link between SDB, glucose intolerance, and insulin resistance. However, studies on the treatment of SDB with continuous positive airway pressure (CPAP) have yielded inconsistent results and overall do not reveal an improvement in the metabolic disturbance after treatment. Although population-based prospective data on the metabolic implications of SDB are still lacking, current data point to an independent association between SDB and impaired glucose homeostasis. Potential mediators of this association include altered adrenergic function, the direct effects of hypoxemia on glucose regulation, and release of proinflammatory cytokines that affect metabolism.