Rationale: Obstructive sleep apnea (OSA), a treatable sleep disorder that is associated with alterations in glucose metabolism in individuals without diabetes, is a highly prevalent comorbidity of type 2 diabetes. However, it is not known whether the severity of OSA is a predictor of glycemic control in patients with diabetes.
Objectives: To determine the impact of OSA on hemoglobin A1c (HbA1c), the major clinical indicator of glycemic control, in patients with type 2 diabetes.
Methods: We performed polysomnography studies and measured HbA1c in 60 consecutive patients with diabetes recruited from outpatient clinics between February 2007 and August 2009.
Measurements and Main Results: A total of 77% of patients with diabetes had OSA (apnea–hypopnea index [AHI] ≥5). Increasing OSA severity was associated with poorer glucose control, after controlling for age, sex, race, body mass index, number of diabetes medications, level of exercise, years of diabetes and total sleep time. Compared with patients without OSA, the adjusted mean HbA1c was increased by 1.49% (P = 0.0028) in patients with mild OSA, 1.93% (P = 0.0033) in patients with moderate OSA, and 3.69% (P < 0.0001) in patients with severe OSA (P < 0.0001 for linear trend). Measures of OSA severity, including total AHI (P = 0.004), rapid eye movement AHI (P = 0.005), and the oxygen desaturation index during total and rapid eye movement sleep (P = 0.005 and P = 0.008, respectively) were positively correlated with increasing HbA1c levels.
Conclusions: In patients with type 2 diabetes, increasing severity of OSA is associated with poorer glucose control, independent of adiposity and other confounders, with effect sizes comparable to those of widely used hypoglycemic drugs.