Obstructive sleep apnea, daytime sleepiness, and type 2 diabetes.

PURPOSE: The purpose of this article is to review the literature on obstructive sleep apnea, resultant daytime sleepiness, and type 2 diabetes mellitus, as the state of evidence exists.
METHODS: A search was conducted on Medline and CINAHL using the search terms sleep apnea syndromes, obstructive sleep apnea, disorders of excessive somnolence, type 2 diabetes mellitus, and insulin resistance. This review includes only published research studies in English, in adults aged 19 years or older. There were 109 citations when the terms were combined, 36 citations that were identified as research studies, no randomized clinical trials, and only 1 qualitative study.
RESULTS: Obstructive sleep apnea and type 2 diabetes share the risk factors of age and central abdominal obesity. Recent studies suggest that obstructive sleep apnea and type 2 diabetes not only frequently coexist but also have a bidirectional association wherein each condition exacerbates the other. The mechanism whereby obstructive sleep apnea affects glucose metabolism is likely repetitive hypoxia and sleep fragmentation, which cause a stress response with increased sympathetic nervous system activity, increased fatigue-causing cytokines, and altered leptin levels that result in weight gain. In addition, daytime sleepiness results in an impaired mood state that may impede diabetes management.
CONCLUSIONS: Type 2 diabetes is prevalent in persons with obstructive sleep apnea, although the direction of causality is unknown. More research, including randomized clinical trials, is needed to determine how obstructive sleep apnea and daytime sleepiness affect persons with type 2 diabetes.