title: Heart rate variability biofeedback decreases blood pressure in prehypertensive subjects by improving autonomic function and baroreflex.
abstract: 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.
  
  
  OBJECTIVE
  The effect of HRV-BF on prehypertension in young adults and its potential mechanism were explored.
  
  
  METHODS
  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 pre-intervention, in the entire process of each session, at postintervention, as well as at a 3-month follow-up.
  
  
  METHODS
  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 (log10-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 ms2) 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 ms2). HRV-BF reduced blood pressure (from 131.7±8.7/79.3±4.7 mm Hg to 118.9±7.3 mm Hg/71.9±4.9 mm Hg, p<0.01), increased BRS (from 7.0±5.9 ms/mm Hg to 15.8±5.3 ms/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 ms2, 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.
authors.affiliation: Department of Physiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, People's Republic of China.
authors.forename: Guiping
authors.initials: G
authors.lastname: Lin
authors.forename: Qiuling
authors.initials: Q
authors.lastname: Xiang
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Fu
authors.forename: Shuzhen
authors.initials: S
authors.lastname: Wang
authors.forename: Sheng
authors.initials: S
authors.lastname: Wang
authors.forename: Sijuan
authors.initials: S
authors.lastname: Chen
authors.forename: Li
authors.initials: L
authors.lastname: Shao
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhao
authors.forename: Tinghuai
authors.initials: T
authors.lastname: Wang
mesh_terms: D000328:Adult; D001341:Autonomic Nervous System / Q000502:physiology*; D017704:Baroreflex / Q000502:physiology*; D001676:Biofeedback, Psychology; D001794:Blood Pressure / Q000502:physiology*; D001945:Breathing Exercises; D005260:Female; D005500:Follow-Up Studies; D005712:Galvanic Skin Response; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D058246:Prehypertension / Q000503:physiopathology / Q000628:therapy*; D055815:Young Adult