There exist real and potential links between the risk factors for and co-morbidity associated with diabetes and sleep apnea. The common occurrence of obesity, hypertension, and disorders of metabolism in each disease is but one example. While the occurrence of sleep apnea with glucose intolerance or insulin resistance could present sampling bias or intersection of common human diseases, an alternative hypothesis is that the events in obstructive sleep apnea (OSA) trigger different, perhaps unique, adaptations in metabolic processes involving insulin action and glucose regulation. Further, clinical studies can be designed to define the extent and potential mechanisms for alterations in insulin and glucose levels in OSA and to determine the sample size and power for a longitudinal study that would follow the relative rates of progression of obesity (including neck size as a body characteristic), breathing abnormalities during sleep, insulin sensitivity, and subsequent risk for non-insulin-dependent diabetes mellitus (NIDDM) and/or symptomatic OSA.