The effect of continuous positive airway pressure on glucose excursions in diabetics with sleep-disordered breathing: the results of continuous glucose monitoring

Abstract

Sleep-disordered breathing (SDB) is often associated with impaired glucose metabolism. The study aimed at assessing immediate effect of CPAP on glucose excursions in type 2 diabetic patients with SDB measured with 72-hour continuous glucose monitoring system (CGMS). 8 type 2 diabetic patients with SDB (men, age 48,13±4,91 years, BMI 34,06±7,41 kg·m–2, HbA1c 7,3±1,4%) underwent 2 overnight polysomnographic examinations including diagnostic night and CPAP night. CGMS was applied on both occasions. Statistical analyses included paired Student's t-test. CPAP decreased apnoea-hypopnoea index (AHI) from 57,64±9,64·h–1 to 8,05±4,42·h–1 (p<0,0001) with significant improvement of saturation. Frequent episodes of sleep apnoea/hypopnoea and severe oxygen desaturation were followed by significant rise in blood glucose of up to 12,3 mmol·l–1. Duration of post-hypoxic hyperglycemia was 50±10,79 min and its climax tended to be appeared up to 45min post-hypoxia. Nocturnal hyperglycemia strongly correlated with severe oxygen desaturation. Nocturnal glucose values were significantly higher during diagnostic night than during CPAP night (8,19±0,99 mmol·l–1 versus 6,77±1,47 mmol·l–1; p<0,0001). CGMS also showed improved preprandial and 1,5-hour postprandial glucose levels for breakfast after CPAP night. The improvement in overall glucose levels was much greater in patients with BMI<30 kg·m–2 than in more obese patients. The results suggest that nocturnal hyperglycemia is closely related to desaturation and CPAP treatment may have an immediate decreasing effect on blood glucose in type 2 diabetic patients with SDB.