Sleep Disordered Breathing (sdb) Is a Preva- Lent and Chronic Condition That Is Charac- Terized by Recurrent Episodes of Upper Airway

1018 SLEEP DISORDERED BREATHING (SDB) IS A PREVALENT AND CHRONIC CONDITION THAT IS CHARACTERIZED BY RECURRENT EPISODES OF UPPER AIRWAY collapse during sleep. It is estimated that approximately 7% of adults in the general population have SDB of at least moderate severity.1 Several epidemiological and clinic-based studies have shown that the prevalence of altered glucose metabolism and type 2 diabetes increases with severity and frequency of selfreported and objective measures of SDB, independent of age and central obesity.2,3 Of the prospective observational studies, two have shown a higher incidence of type 2 diabetes mellitus among habitual snorers,4,5 and one has shown a higher prevalence of type 2 diabetes among those with polysomnographically defined SDB.6 Previous work from the Sleep Heart Health Study (SHHS) has also demonstrated a higher prevalence of impaired fasting glucose, glucose intolerance, and type 2 diabetes mellitus in individuals with SDB independent of body mass index and waist circumference.7 SDB is associated with a number of physiological derangements, including intermittent hypoxemia and sleep fragmentation. Experimental and observational studies that have attempted to uncouple these pathognomonic components of SDB have shown that both hypoxia and disrupted sleep can trigger a cascade of physiological events that may eventually result in altered glucose homeostasis. Increases in autonomic activity8,9 and circulating neuroendocrine hormones such as cortisol10,11 can be elicited by hypoxia and sleep disruption and thus may impair glucose metabolism in SDB. Epidemiologic observations from the SHHS cohort indicate that average oxyhemoglobin saturation during sleep independently correlates with impaired glucose tolerance and type 2 diabetes.7 Thus, measures beside the conventional apnea-hypopnea index may provide a more nuanced understanding of the specific components of SDB that play a role in subsequent pathologies. In order to determine whether disordered breathing events with milder reductions in oxyhemoglobin saturation that are excluded from conventional measures are clinically relevant, it is important to examine the full spectrum of SDB-related events in the context of specific health-related outcomes. The currently recommended criteria for defining a hypopnea include a reduction of airflow that is accompanied by an oxyheFasting gylcemia in sleep-DisorDereD Breathing