Abstract Introduction Positive airway pressure (PAP) is the first line treatment for moderate-severe or symptomatic obstructive sleep apnea (OSA). Randomized controlled trials have established that PAP therapy has beneficial impact on cardiovascular and metabolic functions. However, evidence on the benefits of PAP for preventing major adverse cardiovascular events (MACE) is limited. We aimed to determine the association between PAP utilization and incidence of MACE and all-cause mortality in a large sample of Medicare beneficiaries. Methods Medicare beneficiaries (>65 years) with at least 5 years of consecutive enrollment to part A and B and ≥2 distinct OSA claims were collected from multi-state (Kansas, Missouri, Iowa, Wisconsin, Nebraska, Minnesota, Texas, Utah, North Dakota, South Dakota and Indiana), multi-year (2011-2017) Medicare fee-for-service claims data. We further required at least 1-year enrollment before the first OSA claim. Evidence of PAP utilization and index date was defined based on the first Healthcare Common Procedure Coding System PAP initiation codes (E0601, E0470, E0471) after first OSA diagnosis. MACE was defined as the first occurrence of myocardial infarction, coronary revascularization, stroke, or heart failure (identified by diagnostic and procedure code claims) after PAP initiation. Analyses were adjusted by age at initial OSA diagnosis, sex, race and presence of hypertension, type 2 diabetes, obesity, and evidence of MACE prior to the index date. Results Our sample included 212,445 eligible Medicare beneficiaries with evidence of OSA diagnosis (mean [SD] age 75 [5.7] years; 45.2% women; median [Q1, Q3] follow-up 4 [2.0, 4.9] years at censoring). Five-year MACE cumulative incidence rate was 59.3% and the mortality rate was 17.8%. In adjusted analyses, OSA patients with evidence of PAP utilization (50.8%) had significantly lower MACE incidence risk (HR=0.812; 95%CI=0.803-0.822; p<0.0001) when compared to those without evidence of using PAP. OSA patients with evidence of PAP utilization also had significantly lower mortality risk (HR=0.575; 95%CI=0.560-0.591; p<0.0001). Pre-existing hypertension, type II diabetes and obesity were also significantly associated with increased mortality and MACE risk. Conclusion PAP utilization based on device initiation derived from claims data is associated with lower MACE incidence and mortality in older adults that are Medicare beneficiaries. Support (If Any) American Heart Association (20CDA35310360), Patient-Centered Outcomes Research Institute (RI-CRN-2020-003-IC); NIH CTSA NCATS Frontiers: University of Kansas Clinical and Translational Science Institute (UL1TR002366); Tier 2 grant, University of Missouri.