Sex Differences in the Association Between Cardiac Vagal Control and the Effects of Baroreflex Afferents on Behavior

Abstract

Background: Cardiovascular disease (CVD) is the leading cause of mortality and disability worldwide. While sex differences in CVD have been well documented, the physiological mechanisms of those sex differences remain unclear. As important components of the cardiovascular system, cardiac vagal control and baroreflex serve as mechanisms of sex differences in CVD and are modifiable factors for gender-specific CVD preventions. Methods: Ninety-four healthy adults (18–44 years of age; Mage = 21.09 years; 46 female) were recruited to complete the assessments of heart rate variability (HRV) at a resting baseline and the cardiac timing effect on an R-wave-locked reaction time (RT) task, which were used as the indicator of cardiac vagal control and a novel behavioral measure of baroreflex activity, respectively. HRV metrics (including the root mean square of successive R-R interval differences, high frequency and low frequency heart rate variability, and low frequency-to-high frequency ratio), the cardiac timing effect (the inhibition of RT response at the phase of cardiac systole compared to diastole), and their associations were compared between female and male participants. Results: Female participants showed higher levels of vagally mediated HRV after adjusting for basal resting heart rate. Importantly, the cardiac timing effect on RT responses was positively correlated with vagally mediated HRV among males but not among females. Conclusions: Females and males exhibited different physiological processes to regulate cardiovascular functions and behavioral outcomes. The present findings will help to reduce gender disparities in the preventive care of CVD and improve cardiovascular health for both women and men.

Keywords

• sex differences
• cardiac vagal control
• heart rate variability
• baroreflex
• cardiac timing effect