Objective: Growing evidence indicates that both chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea (OSA) may be related to increased risk of developing metabolic disorder and cardiovascular diseases. However, the association of sleep overlap syndrome (combination of COPD and OSA) with type 2 diabetes is unclear. The aim of this study was to investigate the association between overlap syndrome and prevalence of type 2 diabetes.Methods: In this study, 1 939 patients who completed home sleep test from January 2011 to December 2014 in sleep center of Beijing Anzhen Hospital were retrospectively studied. Sleep events were scored by experienced sleep technicians. COPD were diagnosed according to clinical manifestation and spirometry, while OSA was defined by apnea-hypopnea index ≥15 event/h. All subjects were divided retrospectively into overlap syndrome group (n=1 093), isolated COPD group (n=62), isolated OSA group (n=735), and control group (n=49). The independent association of overlap syndrome with type 2 diabetes prevalence was estimated by using Logistic regression models.Results: Compared with control group and the patients with isolated OSA, the patients with overlap syndrome had significantly higher odds of type 2 diabetes (OR=5.82, 95%CI: 3.23-10.48, P<0.001 and OR=4.35, 95%CI: 2.41-7.88, P<0.001), with significance persisting after adjusting for age, sex, and body mass index as confounding factors (OR=2.69, 95%CI: 1.13-6.52, P=0.026 and OR=3.64, 95%CI: 1.53-8.83, P=0.004). Among those younger than 58 years or female subjects, overlap syndrome had independent association with type 2 diabetes (OR=8.45, 95%CI: 1.46-65.90, P=0.018 and OR=4.39, 95%CI: 1.04-22.50, P=0.044). No significant association was found in the patients ≥58 and male subjects.Conclusion: Sleep overlap syndrome is associated with high prevalence of type 2 diabetes. Further study is needed to verify whether treatment toward overlap syndrome may reduce risk of metabolic disorder, and even decrease long-term risk of complications of diabetes.