Resting Microvascular and Autonomic Function in Relation to Age and Sex Hormone Concentrations

Abstract

This study assessed the influence of estradiol, progesterone, testosterone and age on resting microvascular and autonomic function in younger and older males and females. Microvascular function was assessed with reactive hyperemia using the microvascular function index (MFI) technique (5mins baseline, circulatory occlusion and reperfusion) and was calculated using the area under the curve of pulse waveforms before and after occlusion/reperfusion. Autonomic function was assessed using 5 mins resting heart rate variability (HRV) and paced deep breathing. Multiple linear regressions were conducted for the influence of estradiol, progesterone, testosterone and age on resting HRV variables and MFI. Aging negatively correlated with respiratory sinus arrhythmia (RSA) indicating lower parasympathetic activity and positively correlated with diastolic blood pressure (DBP) and mean arterial pressure (MAP). Estradiol positively correlated with the low frequency/high frequency ratio of HRV, indicating higher sympathetic activity, and DBP and MAP. Progesterone and testosterone were not significantly correlated with any measures.