Abstract： Objective To evaluate the clinical screening value of the Epworth sleepiness scale(ESS)for patients with type 2 diabetes mellitus(T2DM)and obstructive sleep apnea hypopnea syndrome(OSAHS).Methods A total of 399 hospitalized T2DM patients were selected for portable monitoring(PM)and ESS assessment.Based on the presence or absence of OSAHS,the study was divided into a simple T2DM group(T2DM,n=143)and a group with comorbid OSAHS(OSAHS,n=256).According to the apnea-hypopnea index(AHI),the study participants were categorized into a normal group(AHI<5 times/h,n=143),a mild OSAHS group(AHI 5～15 times/h,n=147),a moderate OSAHS group(AHI>15～30 times/h,n=69),and a severe OSAHS group(AHI>30 times/h,n=40).Differences in ESS scores across various OSAHS severity groups were compared.Receiver operating characteristic(ROC)curve analysis was conducted to evaluate the screening value of ESS for OSAHS.Results Body mass index,proportion of obesity,proportion of central obesity,serum creatinine and fasting C-peptide were significantly higher the OSAHS group compared to the non-OSAHS group(P<0.05).Significant statistical differences in ESS scores were observed between the severe and mild OSAHS groups(P=0.006).When an ESS score of≥9 was used as the threshold for screening OSAHS,the concordance rate with PM diagnosis was 40.6%.ROC curve analysis revealed that the area under the curve(AUC)for ESS screening for OSAHS,moderate-to-severe OSAHS,and severe OSAHS,and their respective optimal thresholds(95%CI),were as follows 0.518(95%CI 0.459～0.577,P=0.545),0.571(95%CI 0.507～0.635,P=0.029)and 0.624(95%CI 0.531～0.718,P=0.010),with cutoffs of≥2 points,≥3 points,and≥4 points,respectively.Conclusions An increased ESS score in T2DM patients significantly indicates the likelihood of severe OSAHS.Using an ESS score of≥9 as a threshold to screen for OSAHS is ineffective,whereas an ESS score of≥3 for screening moderate-to-severe OSAHS and≥4 for severe OSAHS has some reference value.