The aim of the study is to determine whether selenoprotein activity and blood renalase level correlate with subclinical hypertensive heart disease and obstructive sleep apnea. The correlation will be assessed using selected electrocardiographic, ultrasound and laboratory indicators.

The study will be conducted in the Department and Clinic of Internal Medicine, Occupational Diseases, Hypertension and Clinical Oncology at Borowska 213 street in Wroclaw. This decision follows the high percentage of people with obstructive sleep apnea and hypertension among those hospitalized in the Clinic and also the wide availability of research tools in the hospital.

150 more patients with hypertension and obstructive sleep apnea will be included in the planned observational study.

The study is observational, research procedures are non-invasive and no additional medical experiment is planned. The study was approved by the Bioethics Committee of the Wroclaw Medical University.

Patients enrolled in the study will be asked to share the results of their previously performed examinations or, in case they do not have any, new examinations will be performed to complement the diagnostic process of hypertension and obstructive sleep apnea.

The planned procedures include: medical interview, physical examination with basic anthropometric measurements (age, height, body weight); biochemical tests including blood selenium, selenoproteins, renalase and creatinine levels; total antioxidant status (TAS), 24-hour Holter electrocardiography, polysomnography, ultrasound assessment of peripheral vascular endothelial function and echocardiography.

Laboratory tests will be performed using commercially available standardized tests. The levels of selenoproteins, renalase and creatinine in the blood, as well as TAS will be determined by ELISA (Enzyme-linked immunosorbent assay) in accordance with the instructions. Blood selenium level will be measured by means of atomic absorption spectrometry (AAS). 24-hour Holter ECG monitoring will be performed using a Lifecard CF recorder, followed by an analysis of the record by the Impresario Solo system (Delmar Reynolds, Hertford, UK). Ultrasound examination will be performed using the ProSound Alpha 6 (Aloka Inc, Tokyo, Japan).

Inclusion Criteria:

• arterial hypertension

Exclusion Criteria:

• age <18
• pregnancy
• refusal to participate in the study

Study participants will be recruited among the patients of the Department of Internal and Occupational Diseases, Hypertension and Clinical Oncology in Wroclaw. 150 more consecutive patients with hypertension and obstructive sleep apnea will be included in the planned observational study.