Introduction: Obstructive sleep apnea (OSA) is associated with increased risk of cardiovascular disease (CVD) but it remains uncertain whether treatment with Continuous Airway Pressure (CPAP) can prevent major cardiovascular (CV) events, especially among older adults. Research Objective: To estimate the incidence of CV events among older Medicare beneficiaries, with and without pre-existing CVD, who initiated CPAP therapy following OSA diagnosis.