The purpose of the current study is to evaluate the clinical and physiologic course of Kyrgyz highlanders with high altitude pulmonary hypertension (HAPH) by performing a longitudinal cohort study. To this end, the investigators will invite the same highlanders who participate din the study in 2017 to undergo follow-up examinations in 2024, in order to allow comparisons of current results with baseline data from 2017.

Inclusion Criteria:

• Permanently living >2500 m
• Written informed consent

Exclusion Criteria:

• Highlanders who cannot follow the study investigations,
• Patients with moderate to severe concomitant lung disease (FEV1<70% or forced vital capacity <70%), severe parenchymal lung disease, heavy smoking >20 cigarettes/day or >20 pack-years.
• Coexistent unstable systemic hypertension or coronary artery disease that required adjustment of medication within the last 2 months
• Regular use of medication that affects control of breathing (benzodiazepines, opioids, acetazolamide)

Highlanders living at Aksay plateau will be invited to participate.