Effects of high-intensity interval training on retinal vessel diameters and oxygen saturation in patients with hypertension: a cross-sectional and randomized controlled trial

Introduction: Arterial hypertension is a global health care burden that affects macrovascular and microvascular structure and function and can promote vascular end organ damage. The aim of this study was to assess the effects of a short-term high-intensity interval training (HIIT) on hypertension-induced retinal microvascular diameter changes in patients with hypertension as add-on treatment to antihypertensive medication.
Methods: Central retinal arteriolar (CRAE) and venular diameter equivalent (CRVE), arteriolar-to-venular diameter ratio (AVR) and retinal oxygen saturation (O2-Saturation) were investigated in 19 normotensive healthy controls (mean age 56±7) and 41 patients with arterial hypertension (mean age 59±7). Patients with arterial hypertension were randomized after baseline assessment to an intervention group (HIIT 3x/week) or a control group which received standard physical activity recommendations. Assessments of retinal vessel biomarkers as well as patients` characteristics were repeated after the intervention period of 8 weeks.
Results: Individuals with normal blood pressure (BP) showed lower body mass index (BMI), body fat, 24h systolic and diastolic BP, higher peak oxygen uptake, wider CRAE (174±17μm vs. 161±17μm, p=0.009) and higher AVR (0.84±0.05 vs. 0.79±0.05, p=0.003) compared to patients with hypertension. The intervention and control group in patients with hypertension both reduced body mass, BMI, and fasting glucose. The intervention group further reduced body fat percentage and increased peak oxygen uptake (VO2peak). No changes in BP were found in either group. The intervention group showed narrower CRVE (β -4.8 [95% CI, -8.85, -0.81] p=0.020) and higher AVR (0.03 [0.01, 0.04] p<0.001) after eight weeks of HIIT compared to the control group. No statistically significant changes in retinal O2-saturation were found in either group.
Conclusion: Short-term HIIT proved to be an effective treatment to ameliorate hypertension-induced retinal arteriolar narrowing in patients with hypertension.
Keywords: hypertension, retinal microvasculature, exercise, high-intensity interval training, blood pressure, oxygen saturation, cardiorespiratory fitness