title: Epidemiological study on the effect of pre-hypertension and family history of hypertension on cardiac autonomic function.
abstract: OBJECTIVE
  This study sought to examine the hypothesis that cardiac autonomic function (CAF) is altered in pre-hypertensive subjects and normotensive subjects with a family history of hypertension (FHH).
  
  
  BACKGROUND
  The findings on the FHH effect in CAF have been inconsistent, and little is known about altered CAF in pre-hypertensive subjects under The Seventh Report of the Joint National Commission on High Blood Pressure criteria of normotension and pre-hypertension.
  
  
  METHODS
  A total of 1,436 community dwellers were classified as having normotension without FHH (NT[-]), normotension with FHH (NT[+]), pre-hypertension, and hypertension. Cardiac autonomic function was determined by standard deviation of RR intervals (SDNN), power spectrum in low frequencies (LF) and high frequencies (HF) and LF/HF ratio in supine position for 5 min, the ratio between the longest RR interval at approximately the 30th beat and the shortest RR interval at approximately the 15th beat after standing (30 max/15 min ratio), and the ratio between the longest RR interval during expiration and the shortest RR interval during inspiration (E/I ratio).
  
  
  RESULTS
  There was a significant difference in all CAF indexes among subjects with NT(-), NT(+), pre-hypertension, and hypertension. Multivariate analyses with an analysis of covariance model showed that 30 max/15 min ratio, E/I ratio, and HF power decreased in subjects with NT(+), pre-hypertension, and hypertension when compared with NT(-) subjects. Pre-hypertensive and hypertensive subjects displayed higher square roots of LF/HF ratios. Only pre-hypertensive subjects had higher LF power.
  
  
  CONCLUSIONS
  Our study provides evidence that CAF plays a role in pre-hypertension and that altered autonomic function is already present in subjects with FHH. An autonomic imbalance shifting with augmented sympathetic tone was more enhanced in pre-hypertension.
authors.affiliation: Department of Family Medicine, National Cheng Kung University, Taiwan, Republic of China.
authors.forename: Jin-Shang
authors.initials: JS
authors.lastname: Wu
authors.forename: Feng-Hwa
authors.initials: FH
authors.lastname: Lu
authors.forename: Yi-Ching
authors.initials: YC
authors.lastname: Yang
authors.forename: Thy-Sheng
authors.initials: TS
authors.lastname: Lin
authors.forename: Jia-Jin
authors.initials: JJ
authors.lastname: Chen
authors.forename: Chih-Hsing
authors.initials: CH
authors.lastname: Wu
authors.forename: Ying-Hsiang
authors.initials: YH
authors.lastname: Huang
authors.forename: Chih-Jen
authors.initials: CJ
authors.lastname: Chang
mesh_terms: D000328:Adult; D001341:Autonomic Nervous System / Q000503:physiopathology*; D018450:Disease Progression; D016021:Epidemiologic Studies; D005260:Female; D020022:Genetic Predisposition to Disease; D006321:Heart / Q000294:innervation*; D006801:Humans; D006973:Hypertension / Q000453:epidemiology* / Q000235:genetics* / Q000503:physiopathology; D008297:Male; D012306:Risk; D012307:Risk Factors; D013624:Taiwan / Q000453:epidemiology; D013997:Time Factors