The goal of this observational study is to assess arterial stiffness and autonomic regulation of blood pressure and heart rate in healthy adults and people with arterial hypertension during orthostatic stress and graded physical exercise. The main objective is to analyze cardiovascular responses to exercise on a cycle ergometer in different subgroups of participants with hypertension.

The study includes healthy young adults and older adults with hypertension. Participants undergo standardized assessments including orthostatic testing, graded exercise testing on a cycle ergometer, electrocardiography, and measurement of arterial stiffness parameters such as pulse wave velocity, as well as other vascular and hemodynamic parameters.

The results of this study are expected to improve understanding of cardiovascular physiology and autonomic regulation in people with hypertension and may contribute to earlier recognition of autonomic dysfunction and improved clinical management.

The autonomic nervous system plays an important role in the regulation of cardiovascular responses to orthostatic stress and physical exercise. Alterations in autonomic regulation may contribute to abnormal blood pressure responses, orthostatic hypotension, or exaggerated blood pressure responses during exercise, particularly in individuals with arterial hypertension.

The aim of this study is to assess arterial stiffness and autonomic regulation of blood pressure and heart rate in healthy individuals and people with arterial hypertension. The study includes healthy young adults and older adults with hypertension who are followed at the Department of Hypertension. Older participants are further categorized into subgroups including hypertension, hypertension with orthostatic hypotension, hypertension with orthostatic hypertension, and hypertension with diabetes mellitus.

All participants undergo standardized cardiovascular evaluation including orthostatic testing, graded exercise testing on a cycle ergometer, electrocardiography, and measurement of arterial stiffness parameters such as pulse wave velocity. During these procedures, blood pressure responses, heart rate variability, and heart rate recovery after exercise are assessed. Additional vascular and hemodynamic parameters are also recorded.

Additional clinical data, including laboratory test results and ambulatory blood pressure monitoring (ABPM) obtained as part of routine outpatient care prior to study participation, are collected from medical records for participants with hypertension with their written informed consent.

The study aims to improve understanding of cardiovascular autonomic regulation and vascular function in both healthy individuals and people with hypertension and related conditions.

Inclusion Criteria:

• Healthy volunteers aged 18-35 years without known acute or chronic disease, non-smokers, body mass index (BMI) 20-24.9 kg/m², and negative orthostatic test
• Participants aged ≥60 years with arterial hypertension followed at the Department of Hypertension
• Hypertension group: controlled arterial hypertension, negative orthostatic test, without diabetes mellitus
• Hypertension with orthostatic hypotension group: controlled arterial hypertension and positive orthostatic test indicating orthostatic hypotension
• Hypertension with orthostatic hypertension group: controlled arterial hypertension and positive orthostatic test indicating a rise in blood pressure during orthostatic testing
• Hypertension with diabetes mellitus group: controlled arterial hypertension and diabetes mellitus without previously diagnosed autonomic dysfunction
• Ability to provide written informed consent

Exclusion Criteria:

• Dementia, neurodegenerative disease, or cognitive impairment preventing understanding of study procedures
• Known cardiovascular disease including heart failure (NYHA II-IV), myocardial infarction within the previous 6 months, clinically significant arrhythmias, or peripheral arterial occlusive disease
• Uncontrolled arterial hypertension
• Change in antihypertensive therapy within the previous 4 weeks
• Presence of a cardiac pacemaker
• Treatment with antiarrhythmic drugs (class I, III, or IV), digoxin, alpha-receptor blockers, or other medications known to significantly affect heart rate variability or autonomic function
• Advanced renal failure (eGFR <30 mL/min/1.73 m²) or advanced liver failure
• Active malignancy
• Body mass index ≥35 kg/m²
• Acute illness within the previous 4 weeks
• Current smoking
• Inability to safely perform exercise testing on a cycle ergometer
• Severe psychiatric disorders without stable treatment
• Pregnancy or breastfeeding
• Participation in another clinical study
• Refusal or inability to provide written informed consent

The study population includes healthy young adults and older adults with arterial hypertension who are followed at the Department of Hypertension, University Medical Centre Ljubljana. Participants with hypertension are categorized into subgroups including hypertension without orthostatic blood pressure abnormalities, hypertension with orthostatic hypotension, hypertension with orthostatic hypertension, and hypertension with diabetes.

Individual participant data will not be shared due to privacy and confidentiality considerations related to clinical data collected in this study.