 Methodology: Prospective cohort study. 1,371 RH patients will be recruited. Ambulatory blood pressure monitoring ABPM, socio-demographic, clinical, OSA-related, biochemical and subclinical organ damage variables and biological samples at baseline will be collected from all the subjects included. A sleep study will be performed in all the subjects at the study inclusion date. Subsequently, the OSA subjects will be managed as per local standard practice. Follow-up variables will be annually collected including blood samples. On the basis of OSA and its treatment, three cohorts of RH subjects will be defined: control non-OSA, OSA-treated and OSA nontreated. 