A 6-month low-sodium diet did not significantly alter heart-rate variability compared to a normal sodium diet in patients with mild to moderate essential hypertension.
RCT (n=80)
Does a 6-month low-sodium diet improve cardiac parasympathetic function measured by HRV in patients with mild to moderate essential hypertension?
A 6-month moderate sodium restriction significantly lowers blood pressure but does not alter heart rate variability, suggesting other mechanisms mediate its antihypertensive effects.
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.
Mäkelä et al. (Thu,) conducted a rct in Mild to moderate essential hypertension (n=80). Low-sodium diet vs. Normal sodium diet was evaluated on Cardiac parasympathetic function as measured by heart-rate variability (HRV). A 6-month low-sodium diet did not significantly alter heart-rate variability compared to a normal sodium diet in patients with mild to moderate essential hypertension.