Regression analysis between resting muscle sympathetic nerve activity (MSNA) burst frequency and central artery stiffness (carotid-femoral pulse wave velocity, PWV) (Panel A) and peripheral artery stiffness (carotid-brachial PWV) (Panel B) in 88 young and middle-age/older men and women. Partial correlation was used to control for mean arterial pressure (MAP) and heart rate (HR) in Model 1; sex, waist/hip ratio (central obesity), MAP, and HR in Model 2; age, sex, waist/hip ratio, MAP, and HR in Model 3.