Effects of Continuous Positive Airway Pressure (CPAP) on Glucose Metabolism
Effects of Continuous Positive Airway Pressure (CPAP) on Glucose Metabolism
Obstructive sleep apnea affects approximately 2-4% of middle-aged adults in the general
 population and is associated with several medical conditions including hypertension and
 coronary artery. Research over the last decade has shown that obstructive sleep apnea may
 also increase the propensity for insulin resistance, glucose intolerance, and type 2 diabetes
 mellitus. Positive airway pressure (PAP) is the first line therapy for the treatment of
 obstructive sleep apnea. While PAP therapy has several favorable effects such as improvements
 in daytime sleepiness and quality of life, it is not clear whether using PAP therapy can
 alter metabolic risk. The overall objective of this study is to examine whether treatment of
 obstructive sleep apnea with positive airway pressure therapy improves glucose tolerance and
 insulin sensitivity. The primary hypothesis of this study is that PAP therapy of obstructive
 sleep apnea will improve in insulin sensitivity and glucose metabolism.
Type 2 diabetes mellitus is one of the most prevalent medical conditions, affecting a
 staggering 246 million people worldwide. Obstructive sleep apnea is a relatively common and
 often undiagnosed condition in the general population. Cross-sectional studies of clinic and
 population-based samples suggest that up to 40% of patients with obstructive sleep apnea have
 type 2 diabetes and up to 75% of patients with type 2 diabetes have obstructive sleep apnea.
 There is increasing evidence that the pathophysiological features of intermittent hypoxia and
 sleep fragmentation may be responsible for altering glucose homeostasis and worsening insulin
 sensitivity. The mechanisms through which obstructive sleep apnea impairs glucose metabolism
 are largely unknown. While intermittent hypoxemia and sleep fragmentation are likely to play
 an essential role, the relative contribution of each in the causal pathway remains to be
 determined. Moreover, whether the adverse effects of intermittent hypoxia and sleep
 fragmentation are mediated through an increase in sympathetic nervous system activity,
 alterations in corticotropic function, and/or systemic inflammation is not known.
 Furthermore, it remains to be determined whether positive pressure therapy for obstructive
 sleep apnea has salutary effects on glucose metabolism. Many of the available studies
 examining the effects of PAP on glucose tolerance and insulin sensitivity are plagued by
 small sample sizes, lack of a control group, and limited data on compliance with positive
 pressure therapy. The current study will assess, using a community-based sample, whether
 treatment of obstructive sleep apnea with positive pressure therapy will improve insulin
 sensitivity, as assessed by the frequently sample intravenous glucose tolerance test (primary
 outcome measure).
Inclusion Criteria:

 -  Ability to give informed consent

 -  Obstructive sleep apnea (untreated)

 -  Ability to comply with study-related assessments

 Exclusion Criteria:

 -  Inability to consent or commit to the required visits

 -  Diabetes mellitus (fasting glucose > 126 mg/dl)

 -  Use of insulin or oral hypoglycemic agent

 -  Weight change of 10% in last six months

 -  Use of oral steroids in the last six months

 -  Severe pulmonary disease (i.e., COPD)

 -  Renal or hepatic insufficiency

 -  Recent Myocardial Infarction (MI) or stroke (< 3 months)

 -  Occupation as a commercial driver

 -  Active substance use

 -  Untreated thyroid disease

 -  Pregnancy

 -  Anemia (Hematocrit < 30%)

 -  Any history of seizures or other neurologic disease

 -  Poor sleep hygiene or sleep disorder other than sleep apnea

 -  Excessive subjective sleepiness (Epworth score > 18)