title: Differences in autonomic activity in individuals with optimal, normal, and high-normal blood pressure levels.
abstract: OBJECTIVE
  We investigated differences in autonomic activity in normotensive individuals having optimal, normal and high-normal blood pressure (BP) levels according to the guidelines of the European Society of Hypertension and European Society of Cardiology (ESH/ESC).
  
  
  METHODS
  The study included 294 normotensive subjects (135 males, 159 females; age range 16 to 75 years) with similar clinical, morphometric, biochemical, electrocardiographic, and echocardiographic features. The subjects were classified into the following BP groups: group 1 (n=113) with optimal BP (<120/80 mmHg); group 2 (n=104) with normal BP (120-129/80-84 mmHg), and group 3 (n=77) with high-normal BP (130-139/85-89 mmHg). All the subjects underwent 24-hour Holter monitoring to obtain heart rate variability (HRV) parameters of 24-hour, daytime, and nighttime periods. Normalized low (LFn) and high (HFn) frequency powers, and logarithmic (Log) values of HRV parameters were also calculated.
  
  
  RESULTS
  On 24-hour Holter monitoring, heart rates were similar in three groups. Compared to group 1 and 2, group 3 exhibited significantly higher LF/HF (p<0.001) and LFn (p=0.001) values, and significantly lower HFn (p=0.001), pNN50 (p=0.001), and rMSSD (p=0.005) values. There were no significant differences between the groups with respect to daytime HRV parameters; however, nighttime LF/HF, LFn, and HFn values were significantly different between the groups. Log LF/HF values obtained during the 24-hour and nighttime periods showed significant differences between group 1 and group 3 (for 24 hours, p<0.001; for night, p=0.001) and between group 2 and group 3 (for 24 hours, p<0.001; for night, p=0.009), but group 1 and group 2 did not differ significantly in this respect (p>0.05).
  
  
  CONCLUSIONS
  These findings suggest that subjects with high-normal BP have increased sympathetic activity and decreased parasympathetic activity, possibly making them more liable to hypertension.
authors.affiliation: Department of Cardiology, Medicine Faculty of Kirikkale University, Kirikkale, Turkey. mtolgadogru@gmail.com
authors.forename: M Tolga
authors.initials: MT
authors.lastname: Doğru
authors.forename: Vedat
authors.initials: V
authors.lastname: Simşek
authors.forename: Omer
authors.initials: O
authors.lastname: Sahin
authors.forename: Nurtaç
authors.initials: N
authors.lastname: Ozer
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001341:Autonomic Nervous System / Q000502:physiology* / Q000503:physiopathology; D001794:Blood Pressure; D004452:Echocardiography; D015716:Electrocardiography, Ambulatory / Q000379:methods; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D006973:Hypertension / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010808:Physical Examination