Impact of obstructive sleep apnea complicated with type 2 diabetes on long-term cardiovascular risks and all-cause mortality in elderly patients

BACKGROUND: The prognostic significance of obstructive sleep apnea (OSA) in elderly patients with type 2 diabetes is unclear. The aim of this study was to determine the risk of cardiovascular disease (CVD) and mortality in elderly patients with OSA complicated with type 2 diabetes compared to patients with OSA without type 2 diabetes. METHODS: From January 2015 to October 2017, 1113 eligible elderly patients with OSA, no history of cardiovascular, ≥60 years of age, and complete follow-up records were enrolled in this consecutive multicentre prospective cohort study. All patients had completed polysomnography (PSG) examinations. An apnoea-hypopnoea index of ≥5 events per hour recorded by polysomnography was defined as the diagnostic criterion for OSA. We collected baseline demographics, clinical characteristics, sleep parameters and follow-up outcomes. The primary aim of this study was to identify the risk of incident major adverse cardiovascular events (MACE). Secondary outcomes were all-cause mortality, components of MACE and a composite of all events. Kaplan-Meier survival analysis and Cox proportional hazards models were used to evaluate whether type 2 diabetes was associated with incident events. RESULTS: A total of 266 (23.9%) patients had OSA complicated with type 2 diabetes. MACE occurred in 97 patients during the median 42-month follow-up. Kaplan-Meier survival curves indicated a significant relationship between type 2 diabetes and MACE (log-rank P = 0.003). Multivariable Cox regression analysis showed that type 2 diabetes increased the risk of MACE (HR = 1.64, 95% CI:1.08–2.47, P = 0.019), hospitalisation for unstable angina (HR = 2.11, 95% CI:1.23–3.64, P = 0.007) and a composite of all events in elderly patients with OSA (HR = 1.70, 95% CI:1.17–2.49, P = 0.007). However, there were no significant differences in the incidence of cardiovascular death, all-cause mortality, MI and hospitalisation for heart failure between patients with and without diabetes (P > 0.05). The subgroup analysis demonstrated that females (AHR = 2.46, 95% CI:1.17–5.19, P = 0.018), ≥ 70 years (AHR = 1.95, 95% CI:1.08–3.52, P = 0.027), overweight and obese (AHR = 2.04, 95% CI:1.29–3.33, P = 0.002) with mild OSA (AHR = 2.42, 95% CI: 1.03–5.71, P = 0.044) were at a higher risk for MACE by diabetes. CONCLUSION: OSA and type 2 diabetes are interrelated and synergistic with MACE, hospitalisation for unstable angina and a composite of all events development. Overweight and obese females, ≥ 70 years with mild OSA combined with type 2 diabetes presented a significantly high MACE risk. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12877-021-02461-x.