HighlightsAdherence to CPAP therapy in patients with severe obstructive sleep apnea and cardiovascular diseases can be predicted using a model that includes the desaturation index and anxiety. Aim. To evaluate the results of CPAP therapy (Continuous Positive Airway Pressure) in cardiac patients with severe obstructive sleep apnea (OSA) and to identify factors predicting adherence to CPAP therapy using prospective follow-up data.Methods. The study included 52 patients with severe OSA (82.7% men, 55.6 ± 8.8 years) examined in 2019–2022, the data was collected from the registry of cardiac patients with OSA (n = 138). Arterial hypertension was diagnosed in 96.1% of patients, coronary artery disease (CAD) was diagnosed in 42.3% of patients, chronic heart failure was diagnosed in 86.5% of patients. Clinical and laboratory parameters, data from OSA screening scales, overnight pulse oximetry, diagnostic scales of anxiety, depression, quality of life and cognitive function were assessed before the start of CPAP therapy and 12.3 ± 7.0 months after its start. 8 patients adequately used CPAP therapy (group with CPAP) and 44 patients either refused to use it or used it inadequately (group without CPAP).Results. When comparing the groups at baseline, there were no differences in age, gender, body mass index and clinical characteristics. Predictors of adherence to CPAP therapy were a higher desaturation index (odds ratio (OR) 1.264, 95% confidence interval (CI) 1.017–1.569, p = 0.034) and manifestations of anxiety (OR 1.056, 95% CI 1.01–1.115, p = 0.049). The sensitivity of the model was 85.7%, specificity was 78%, and area under the ROC curve was 0.843 (95% CI 0.712–0.974, p = 0.004). There were no new cases of CAD in the group with CPAP, in the group without CPAP, 5 new cases of CAD developed during follow-up.Conclusion. Adherence to CPAP therapy in patients with severe OSA and cardiovascular disease can be predicted with high sensitivity and specificity using the model that includes the desaturation index and anxiety. Supposedly, CPAP therapy is relevant for secondary prevention of coronary artery disease.