Methods. In the developing study, three variables were found as predictors of mayor outcomes and were incorporated in a multidimensional index: the apnea-hypopnea index, the severity of daytime sleepiness as quantified by the Epworth questionnaire and the presence of current cardiovascular disease. The index (OSA-SCORE) has a value between 0 (less risk) to 5 (more risk). For each point, a significant increment in the risk of death was found. In the retrospective validation study, a number of potential variables will be recorded, all of them also predictors of major outcomes. Data will be recorded by trained personnel on-site at the respiratory Sleep Units around the country. The final cohort will include 1100 subjects aged > 18 years . The observation time will be considered since the time at diagnosis to fatal event and the patient will be censored when non-invasive ventilation was started or at the recorded time if the patient is alive. The primary outcome is all-cause death.