COVID-19 induces profound vascular endothelial dysfunction, the long-term impact of which is unknown. Moreover, recovery from COVID-19 is delayed in a substantial number of COVID-19 patients (~ 30-40%) and characterized by persistent symptoms of fatigue, weakness, and neurocognitive deficits commonly referred to as “long-COVID”. The overall objective of this project is to evaluate the long-term consequences of COVID-19 in older Veterans and provide scientifically sound recommendations for vascular endothelial function-based rehabilitation in older Veterans after COVID-19 and older Veterans in general. The central hypothesis is that, given the fundamental role of oxidative stress and inflammation in long-COVID, vascular endothelial dysfunction following COVID-19 will be associated with long-term negative impacts on health and exercise-based rehabilitation with mitochondria-targeted antioxidant (Mito-Q) supplementation will synergistically improve peripheral and cerebral vascular endothelial dysfunction in older Veterans while convalescing from COVID-19. The rationale for this project is that improving COVID-19-induced vascular endothelial dysfunction by decreasing oxidative stress and inflammation with optimized rehabilitation has the potential to improve health in Veterans with long-COVID, and improve both morbidity and mortality in older Veterans. The central hypothesis will be tested by pursuing two Specific Aims: 1) determine the time course and health risks of vascular endothelial dysfunction in older Veterans with long-COVID, older Veterans who are COVID-recovered, and older Veterans who never had COVID and 2) determine the efficacy of exercise-based rehabilitation with and without Mito-Q supplementation to improve vascular endothelial function in older Veterans with long-COVID, older Veterans who are COVID-recovered, and older Veterans who never had COVID. Under Specific Aim 1, single passive leg movement (sPLM), flow-mediated dilation (FMD), and the breath-hold acceleration index (BHAI) will be used to evaluate microvascular, conduit artery, and cerebral vascular endothelial function in older patients twice annually for 4 years to determine long-term impact of COVID-19 on vascular endothelial function. Additionally, patient health risks, negative outcomes, [neurocognitive function, and pulmonary function] will be tracked during this time to determine the prognostic ability of the peripheral and cerebral vascular endothelial function assessments. For Specific Aim 2, microvascular (sPLM), conduit artery (FMD), and cerebral (BHAI) vascular endothelial function will be assessed before and after either exercise-based rehabilitation or exercise-based rehabilitation combined with Mito-Q supplementation to determine their efficacy to improve peripheral and cerebral vascular endothelial function in COVID-impacted Veterans and older Veterans in general. The research proposed in this application is innovative because it focuses on lead therapeutic ca...