Racial disparities exist in the development of high blood pressure and heart and kidney disease. Over the last 25 years, African American (AA) adults have had the greatest prevalence of high blood pressure compared to any other racial identity group in the United States. In 2015, \~100,000 AA adults died from heart disease, accounting for one-third of all deaths in this population. AA adults also have a 2-3-times higher lifetime risk for developing end-stage kidney disease compared to White (W) adults. Further, advanced age is one of the most significant risk factors for developing high blood pressure, heart disease, and kidney disease. In 2013-2014, \~29% of deaths of adults aged 65 years or older were caused by heart disease, the leading cause of death in this population.
Elevated sympathetic nervous system activity is associated with increased incidence of heart and kidney disease. Physical activity, such as exercise, acutely increases sympathetic nervous system activity, notably directed towards the kidneys, resulting in reflex narrowing of small blood vessels inside the kidneys. This response reduces blood flow to the kidneys to deliver greater blood flow to the active skeletal muscles. Most of the research studies in this area have involved participant groups who were wholly or predominantly of W racial identity, with smaller proportions of individuals of other racial identities. This underrepresentation of non-W participants, including AA adults, has occurred despite the known health disparities such as the greater incidence of high blood pressure and heart disease and kidney disease experienced by these populations.
A larger decrease in kidney blood flow during exercise has been observed in patients with heart failure and peripheral arterial disease compared to healthy adults. However, it is not known whether the decrease in kidney blood flow during exercise is larger in healthy older AA adults compared to other racial identity groups. Given the greater level of chronic psychological stress often experienced by AA adults due to systemic racism and social and environmental factors, the associated cumulative negative impact on cardiovascular health could underlie a physiological difference observed between AA and W adults. Therefore, it is hypothesized that healthy older AA adults will exhibit a larger decrease in kidney blood flow during exercise compared to W adults. This greater response in older AA adults could be a significant factor contributing to the higher rates of heart and kidney disease in this population given the negative effect that this larger response could have over time, highlighting the clinical significance of this area.
The goal of this project is to collect preliminary data regarding the kidney blood flow response to exercise in healthy older AA compared to W adults. This will be achieved through the innovative use of Doppler ultrasound to noninvasively measure kidney blood flow in real time during cycling exercise in 6 healthy older AA adults and 6 healthy older W adults. The preliminary data collected in this project will be used to strengthen future proposals to secure external funding to complete this project on a larger scale. Findings from a larger-scale project will have important implications for developing preventative strategies to reduce the elevated risk of developing heart and kidney disease in the AA population.
