PAH-SDB: Sleep-Disordered Breathing and Outcomes in Pulmonary Arterial Hypertension

Inclusion Criteria: * Age ≥18 years at enrollment. * Diagnosis of WHO Group 1 pulmonary arterial hypertension established by right heart catheterization using contemporary hemodynamic criteria: mean pulmonary artery pressure \>20 mmHg at rest, pulmonary arterial wedge pressure ≤15 mmHg, and pulmonary vascular resistance \>2 Wood units, with clinical classification consistent with Group 1 PAH. * PAH etiology may include idiopathic, heritable, drug/toxin-associated, connective-tissue-disease-associated, congenital-heart-disease-associated PAH after appropriate clinical classification, portal-hypertension-associated PAH, HIV-associated PAH, or other recognized Group 1 PAH subtypes. * Clinically stable enough to undergo overnight sleep/cardiorespiratory monitoring, as judged by the treating team. * Able and willing to provide written informed consent and participate in longitudinal follow-up. * Enrollment at a participating center with availability of the required baseline PAH dataset and a technically interpretable protocol-standardized sleep recording. Exclusion Criteria: * Pulmonary hypertension predominantly attributable to left heart disease (Group 2), lung disease and/or hypoxia (Group 3), chronic thromboembolic pulmonary hypertension or other pulmonary artery obstruction (Group 4), or unclear/multifactorial mechanisms (Group 5). * Pulmonary veno-occlusive disease / pulmonary capillary hemangiomatosis when the clinical phenotype is considered separately from conventional PAH for the planned analysis, unless the protocol intentionally includes this subgroup and prespecifies it as a distinct stratum. * Acute decompensated right heart failure, cardiogenic shock, severe active infection, or another acute condition that would make the baseline sleep recording unrepresentative or unsafe; these patients may be reconsidered after stabilization. * Current hospitalization primarily for an acute non-PAH illness likely to substantially distort nocturnal respiratory physiology. * Inability to obtain an adequate baseline sleep/cardiorespiratory recording after protocol-defined repeat attempt, unless the participant is retained in a registry-only stratum for non-sleep analyses. * Inability to provide informed consent or anticipated inability to complete meaningful follow-up. * Any other condition that, in the investigator's judgment, would prevent reliable study participation or data interpretation.