Study protocol

The following measurements will be performed during your visits at the DSBG:

Retinal measurements

Large arteries

Physical fitness

Physical activity

Other

Here you will find the aim, procedure and duration of each measurement.

Static Retinal Vessel Analysis

Aim: The Static Retinal Vessel Analysis examines the diameters of the small arteries and veins of the retina, which are ~100-250 µm. The diameters of the retinal vessels and the ratio of arteries to veins (AV ratio) reflect the risk for cardiovascular diseases. Thereby, the so-called cardiovascular risk increases especially with narrow retinal arteries and wide veins. With this simple method, the health of the smallest vessels (microvascular) can be assessed representatively by looking into the eye. The examination is used in prevention to screen cardiovascular risk and to monitor the progress of drug and non-drug therapies (physical activity and medical training therapy).

Procedure: The retinal vascular analysis is an eye examination similar to what you know from the ophthalmologist. The images of the ocular fundus are stored and evaluated in a standardized way at a later time by an experienced examiner using special software.

Duration: 5 to 10 minutes.

Dynamic Retinal Vessel Analysis

Aim: To examine the flicker light induced dilation of the artery and the vein. Dynamic retinal vessel analysis enables the examination of microvascular dysfunction.

Procedure: The measurement is performed with Dynamic Vessel Analyzer (DVA). The measurement requires the participant to simply sit still, while DVA records the vascular response that vessels have on flicker light. During the measurement, the function of the smallest vessels and their regulatory mechanisms are investigated.

Duration: Approximately 15 minutes, including 5-10 min preparation and 350 seconds measurement.

Laser Speckle Flowgraphy

Aim: Laser Speckle Flowgraphy (LSFG) is a diagnostic method for the assessment of blood flow in the optic nerve head and retina. LSFG offers an easily accessible way to investigate the ocular circulation and visual field sensitivity.

Procedure: The measurement requires the participant to sit still, while the blood flow in the fundus is being recorded for 4 seconds.    

Duration: Approximately 10 minutes, including preparation and 4-second measurement.   

Wall-to-Lumen Ratio

Aim: Wall-to-Lumen Ratio describes the ratio between the thickness of the blood vessel wall to the size of the inner lumen (= the hollow space where blood flows) of the blood vessel. The ratio can be used as an indicator of remodeling or thickening of the blood vessel, which can be associated with various vascular diseases. Changes in the Wall-to-Lumen Ratio can affect blood flow and overall vascular function.

Procedure: During the measurement, the participant is required to sit still, while a total of 11 images of the retina are being taken.

Duration: Approximately 10 minutes. 

Bayliss-Effect

Aim: The Bayliss-Effect refers to the ability of small blood vessels to regulate their own diameter in response to changes in blood pressure to help maintain a relatively constant level of blood flow to tissues and organs. When blood pressure in these vessels rises, the smooth muscle cells in their walls contract, leading to narrowing of the vessel’s diameter. This helps limit the increase in blood flow and pressure, preventing damage to the delicate capillaries downstream and maintaining tissue perfusion at an appropriate level. Conversely, when blood pressure decreases, the smooth muscle cells relax, causing a widening of the vessel’s diameter. The widening allows for more blood to flow through, which helps maintain tissue perfusion even when blood pressure drops.

Procedure: During the measurement, one segment of participants retinal arteries and venules will be measured continuously over ~6 minutes. Blood pressure will be measured during the whole measurement using a finger cuff. The examination proceeds in the following phases:

  1. Baseline: The baseline state of the retinal vessels is recorded for 50 seconds.
  2. Handgrip 30%: The participant will be asked to press the handgrip with 30% from their maximum for 30 seconds. Retinal vessels’ response to the increased blood pressure is being measured continuously.
  3. Handgrip 100%: The participant will be asked to press the handgrip with maximum effort for 30 seconds. Retinal vessels’ response to the increased blood pressure is being measured continuously.
  4. Rest: 80 second of rest.
  5. Repetition: Phases 2-4 are repeated.

Duration: Approximately 20 minutes.

Flow Mediated Dilation

Aim: To examine the artery’s ability to dilate in response to increased blood flow.

Procedure: The measurement is carried out with harmless ultrasound on the brachial artery. The blood flow in the forearm is restricted for 5 minutes, using a blood pressure cuff. The cuff is inflated above systolic blood pressure, so that only little blood can flow into the forearm. This is harmless to the arm and does not usually cause any pain. The diameter of the artery is measured before and after 5 minutes of congestion and for 3 minutes after the congestion is released. The measurement is made with self-adjusting ultrasound heads and automatic migration detection software, which together provide the most reproducible measurement results.

Duration: Approximately 30 minutes, including 5-10 min preparation, 15 min resting phase, and 10 min measurement phase.

Pulse Wave Velocity

Aim: To examine arterial stiffness, or in other words, to measure the rate at which pressure waves move down the vessel. The basic concept behind Pulse Wave Velocity is that it provides information about the stiffness or elasticity of the arteries. Stiffer arteries transmit the pulse wave more rapidly, while more elastic arteries slow it down.

Procedure: The measurement requires the participant to simply stay in a comfortable lying position. After a short resting period, a blood pressure cuff will be placed on participants’ right upper thigh. Carotid pulse will be measured using a tonometer while the femoral pulse is measured through pulsations in the thigh cuff. The measurement is completely non-invasive.

Duration: Approximately 15 minutes.

Cardiopulmonary Exercise Test

Aim: Cardiopulmonary Excercise Test (CPET) is a medical diagnostic procedure that combines the assessment of cardiovascular (heart) and pulmonary (lung) function with exercise testing. The test is performed on a stationary bicycle and is used to evaluate the participants’ overall cardiopulmonary fitness, as well as to diagnose and assess various cardiovascular and respiratory conditions.

Procedure: : During cardiopulmonary exercise testing, the uptake of oxygen and the production of carbon dioxide is measured by means of a face mask under defined physical stress on a bicycle ergometer. During the test, after a short warm-up phase, the load (by means of wattage) is continuously increased until subjective exhaustion. This usually takes 6-12 minutes. During this time, your heart activity is recorded with an ECG. If you experience any discomfort during the test, the test will be stopped immediately.

Duration: Approximately 30 minutes.

Accelerometry

Aim: The objective measurement of sporting and everyday movement with a movement sensor is indispensable today for a well-founded recording of physical activity. Only on this basis can reliable, individual statements about physical activity be made. Compared to a questionnaire, objective movement measurement is much more precise, because people usually estimate themselves to be much more active with a questionnaire than they really are.

Procedure: The accelerometer is worn like a watch on the wrist for 24 hours a day over the entire measurement period (8 days). It is not a hindrance to everyday or office activities and is hardly noticeable to others. It is kept on for showering or swimming. The device does not need to be charged. The device is then worn for 8 days and all activities are recorded during this time. The accelerometer is returned on your second visit to the DSBG.

Questionnaires

Aim: Using digital questionnaires, data about participants daily physical activity, health-related quality of life and vision related quality of life is assessed. 

Duration: Approximately 30 minutes.

Blood Sampling

Aim: The aim of the blood sampling is to monitor the effects of the intervention and to monitor participants’ overall health. 

Procedure: Blood will be drawn in a fastened state from the cubital fossa while the participant sits or is in a lying position.

Duration: Approximately 10 minutes.

24h Ambulatory Blood Pressure Measurement

Aim: 24 Hour Ambulatory Blood Pressure Measurement is a valuable tool in diagnosing and managing hypertension, assessing blood pressure variability, and improving overall cardiovascular risk assessment. It provides a more comprehensive understanding of a patient’s blood pressure profile compared to isolated measurements taken in a clinical setting.

Procedure: The participant will be equipped with a 24 h blood pressure monitor and instructed on how to use it. The participant will wear this device for a total of 24 hours.

Duration: 24 hours.