Heart Rate Variability Biofeedback Decreases Blood Pressure in Prehypertensive Subjects by Improving Autonomic Function and Baroreflex

Background: Individuals with prehypertension are at risk of hypertension and cardiovascular diseases, and yet efficient interventions are lagging behind. Studies indicate that heart rate variability-biofeedback (HRV-BF) increases HRV and baroreflex sensitivity (BRS) as well as reduces related pathological symptoms, suggesting potentially beneficial effects of HRV-BF on prehypertension, but little is known about these effects. In this study, these effects were investigated and their mechanisms were explored. Objectives: The effect of HRV-BF on prehypertension in young adults and its potential mechanism were explored. Design: Forty-three (43) individuals with prehypertension were recruited and classified into three categories: HRV-BF group, slow abdominal breathing group, and control group. All groups were assessed with measurements of noninvasive blood pressure (BP), BRS, respiration, and galvanic skin response (GSR) at preintervention, in the entire process of each session, at postintervention, as well as at a 3-month follow-up. Interventions: Subjects participated in a 10-session HRV-BF protocol or simple slow abdominal breathing protocol conducted over 5 weeks. A 3-month follow-up was also performed on these individuals. Results: The incidence of prehypertension was as high as 14.5% in young college students. Individuals with prehypertension were lower in BRS (7.5+/-5.2 ms/mm Hg) and HRV (log(10)-transformed of the standard deviation of normal-to-normal beats [SDNN] = 1.62+/-0.13 ms, lgTotal power of spectral density in the range of frequencies between 0 and 0.4Hz (TP) = 8.02+/-0.55 ms(2)) than those with normal blood pressure (BRS = 18.4+/-7.4 ms/mm Hg, lgSDNN = 1.79+/-0.10 ms, lgTP = 8.68+/-0.85 ms(2)). HRV-BF reduced blood pressure (from 131.7+/-8.7/79.3+/-4.7mm Hg to 118.9+/-7.3mm Hg/71.9+/-4.9mm Hg, p < 0.01), increased BRS (from 7.0+/-5.9 ms/mm Hg to 15.8+/-5.3ms/mm Hg, p < 0.01) and increased HRV (lgSDNN from 1.61+/-0.11 to 1.75+/-0.05 ms, and lgTP from 8.07+/-0.54 to 9.08+/-0.41 ms(2), p < 0.01). These effects were more obvious than those of the slow-breathing group, and remained for at least 3 months. HRV-BF also significantly increased vagus-associated HRV indices and decreased GSR (indices of sympathetic tone). Conclusions: These effects suggest that HRV-BF, a novel behavioral neurocardiac intervention, could enhance BRS, improve the cardiac autonomic tone, and facilitate BP adjustment for individuals with prehypertension.