Abstract： Background:For patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) and type 2 diabetes mellitus (T2DM),the night sleep interruption and intermittent hypoxia due to apnea or hypopnea may induce glycemic excursions and reduce insulin sensitivity.This study aimed to investigate the effect of continuous positive airway pressure (CPAP) therapy in patients with OSAHS and T2DM.Methods:Continuous glucose monitoring system (CGMS) was used in 40 patients with T2DM and newly diagnosed OSAHS.The measurements were repeated after 30 days of CPAP treatment.Subsequently,insulin sensitivity and glycohemoglobin (HbA1c) were measured and compared to the pretreatment data.Results:After CPAP therapy,the CGMS indicators showed that the 24-h mean blood glucose (MBG) and the night time MBG were significantly reduced (P ＜ 0.05 and P =0.03,respectively).The mean ambulatory glucose excursions (MAGEs) and the mean of daily differences were also significantly reduced (P ＜ 0.05 and P =0.002,respectively) compared to pretreatment levels.During the night,MAGE also significantly decreased (P =0.049).The differences between the highest and lowest levels of blood glucose over 24 h and during the night were significantly lower than prior to CPAP treatment (P ＜ 0.05 and P =0.024,respectively).The 24 h and night time durations of high blood glucose (＞7.8 mmol/L and ＞ 11.1 mmol/L) decreased (P ＜ 0.05 and P ＜ 0.05,respectively) after the treatment.Inaddition,HbA1c levels were also lower than those before treatment (P ＜ 0.05),and the homeostasis model assessment index of insulin resistance was also significantly lower than before CPAP treatment (P =0.034).Conclusions:CPAP therapy may have a beneficial effect on improving not only blood glucose but also upon insulin sensitivity in T2DM patients with OSAHS.This suggests that CPAP may be an effective treatment for T2DM in addition to intensive diabetes management.