Autonomic nervous system influences on beat-to-beat blood pressure variability in healthy young adults

Based on evidence from 24-h and visit-to-visit blood pressure (BP) monitoring, recent laboratory-based studies have begun investigating beat-to-beat average real variability (ARV) in BP as a prognostic indicator of cardiovascular risk. However, beat-to-beat BP ARV may be influenced by adaptive parasympathetic modulation of heart period, particularly in young, otherwise healthy adults. This profound modulation of heart rate between consecutive cardiac cycles might paradoxically increase ARV, yet the autonomic underpinnings of BP ARV remain uncharacterized. Herein, we characterize the association between beat-to-beat BP variability (BPV), estimated cardiac parasympathetic modulation via heart rate variability (HRV), and muscle sympathetic nerve activity (MSNA) in humans. Recordings of continuous BP (finger photoplethysmography) and heart rate (HR; electrocardiogram) were obtained in 145 healthy young adults [97 M, 48 F; age: 22 ± 4 yr; body mass index (BMI): 24 ± 3 kg/m²] across a 10-min resting period. Recordings of MSNA (microneurography) were available in 103 participants. BP ARV, standard deviation (SD), and coefficient of variation (CV) were used to quantify BPV. Time and frequency-domain HRV were associated positively with BP ARV (rs = 0.388-0.820, Ps < 0.001), but not SD or CV (Ps > 0.05). Sympathetic baroreflex sensitivity (sBRS) was weakly correlated with mean arterial pressure ARV (r = 0.225, P = 0.025) and unrelated to systolic and diastolic BP ARV (P > 0.05) but negatively associated with BPV quantified as the SD or CV (rs = 0.412-0.514, P < 0.001). The positive association between BP ARV and resting HRV suggests that elevated BP ARV in young healthy adults is influenced by cardiac parasympathetic modulation, whereas other traditional measures of BPV are not as affected.NEW & NOTEWORTHY Beat-to-beat blood pressure variability quantified as the average real variability (ARV) is positively associated with resting heart rate variability (HRV) and cardiovagal baroreflex sensitivity in healthy young adults. As higher HRV and cardiovagal baroreflex sensitivity are commonly associated with positive cardiovascular health outcomes, the association between HRV, and cardiovagal baroreflex sensitivity, with beat-to-beat blood pressure ARV suggests that higher beat-to-beat blood pressure ARV is influenced by cardiac parasympathetic modulation in young healthy adults.