The effects of extremely low-frequency electromagnetic fields (ELF-EMFs) on blood pressure (BP) are controversial. In this double-blind, randomized, sham-controlled study, we examined the effects of repeated exposure to a 1-μT ELF-EMF on BP in 20 humans with mild-to-moderate hypertension. Subjects were randomly assigned to either the ELF-EMF group or the sham group. Subjects in the ELF-EMF group were exposed to an ELF-EMF (6- and 8 Hz, respectively, peak magnetic field 1 μT, peak electric field 10 Vm(-1)) for at least two 10- to 15-min sessions per week, over a period of 4 weeks. In the sham group, the EMF-generating apparatus was not active. We obtained systolic and diastolic BP (SBP and DBP, respectively) measurements at registration and before and after each ELF-EMF exposure session. Subjects in the ELF-EMF and sham groups had mean ages of 52.8 and 55.1 years, and were exposed to a mean of 9.9 and 9.0 sessions, respectively. There was a significant difference between the ELF-EMF and sham groups with respect to change in SBP value between baseline and the end of the exposure regimen (P=0.02), but not with respect to change in DBP (P=0.21). There were no adverse events other than mild paresthesia of the hands of two subjects in the ELF-EMF group. Our results suggest that repeated exposure to an ELF-EMF has a BP-lowering effect on humans with mild-to-moderate hypertension.

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