Background: Although obstructive sleep apnea (OSA) has been linked to insulin resistance and glucose intolerance, it is unclear whether there is an independent association between OSA and diabetes mellitus (DM) and whether all patients with OSA are at risk. The objective of this study was to determine the association between OSA and DM in a large cohort of patients referred for sleep diagnostic testing.
Methods: Cross-sectional analysis of participants in a clinic-based study conducted between July 2005 and August 2007. Diabetes was defined by self-report and concurrent use of diabetic medications (oral hypoglycemics and/or insulin). Sensitivity analysis was performed using a validated administrative definition of diabetes. Obstructive sleep apnea was defined by the respiratory disturbance index (RDI) using polysomnography or ambulatory monitoring. Severe OSA was defined as an RDI >30 hr-1. Subjective sleepiness was defined as an Epworth Sleepiness Scale score ≥ 10.
Results: Complete data was available in 2149 patients. The prevalence of DM increased with increasing OSA severity (p<0.001). Severe OSA was associated with DM following adjustment for patient demographics, weight, and neck circumference (Odds Ratio 2.18; 95% CI: 1.22, 3.89; p<0.01). Following a stratified analysis, this relationship was observed exclusively in sleepy patients: Odds Ratio 2.59 (95% CI: 1.35, 4.97) vs. non-sleepy patients: 1.16 (95% CI: 0.31, 4.37).
Conclusions: Severe OSA is independently associated with DM in patients who report excessive sleepiness. Future studies investigating the impact of OSA treatment on DM may wish to focus on this patient population.