title: The effects of a 6-month sodium restriction on cardiac autonomic function in patients with mild to moderate essential hypertension.
abstract: BACKGROUND
  The blood pressure-lowering mechanism of low-sodium diet is not fully understood.
  
  
  METHODS
  We assessed the effects of salt restriction on cardiac parasympathetic function as measured by heart-rate variability (HRV) in mild to moderate hypertensive patients. Eighty patients were randomized to a 6-month low- (N = 40) or normal (N = 40) sodium diet and a 24-h electrocardiogram (ECG) was carried out in the beginning of the study and at 6 months. Five time-domain and six frequency-domain HRV variables were analyzed: mean RR interval, standard deviation of normal RR intervals, mean of the standard deviations of all RR intervals for 5-min segments of the entire recording, percentage of differences between adjacent normal RR intervals exceeding 50 ms, square root of the mean of squared differences between adjacent normal RR intervals, total (0.01-0.40 Hz), high frequency (HF, 0.15-0.40 Hz), low frequency (LF, 0.04-0.15 Hz), very LF (0.01-0.04 Hz) and LF/HF ratio.
  
  
  RESULTS
  Although blood pressure diminished significantly (systolic blood pressure (SBP) from 149.9 +/- 14.7 mm Hg to 130.3 +/- 11.8 mm Hg, P < 0.001 and diastolic blood pressure (DBP) from 98.0 +/- 6.4 mm Hg to 87.1 +/- 6.2 mm Hg, P <0.001) after 6 months in the salt reduction group, no significant differences in the change between the groups could be detected.
  
  
  CONCLUSIONS
  A moderate, prolonged dietary sodium restriction does not alter HRV. Therefore, mechanisms other than cardiac autonomic mechanisms are likely to predominate in the blood pressure-lowering effect of salt restriction.
authors.affiliation: Department of Medicine, Turku University Hospital, Turku, Finland. Petri.Makela@tyks.fi
authors.forename: Petri
authors.initials: P
authors.lastname: Mäkelä
authors.forename: Tero
authors.initials: T
authors.lastname: Vahlberg
authors.forename: Ilkka
authors.initials: I
authors.lastname: Kantola
authors.forename: Risto
authors.initials: R
authors.lastname: Vesalainen
authors.forename: Antti
authors.initials: A
authors.lastname: Jula
mesh_terms: D000328:Adult; D001341:Autonomic Nervous System / Q000187:drug effects / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D004039:Diet, Sodium-Restricted; D004562:Electrocardiography; D005260:Female; D006321:Heart / Q000187:drug effects / Q000294:innervation* / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D006973:Hypertension / Q000178:diet therapy / Q000503:physiopathology* / Q000652:urine; D008297:Male; D008875:Middle Aged; D012964:Sodium / Q000494:pharmacology / Q000652:urine; D013997:Time Factors
chemical_list: D012964:Sodium