Heart rate variability responses to 26 GHz millimeter-wave exposure in healthy young adults

The ongoing expansion of 5 G networks, using millimeter waves like the 26 GHz frequency band, calls for a better understanding of their potential health effects. In this context, the acute effects of 26 GHz exposure on heart rate variability (HRV), a non-invasive marker of autonomic nervous system activity, were evaluated in healthy young adults. Using a triple-blind, randomized crossover design, 31 participants were exposed to both real and sham 26 GHz 5 G new radio modulated radiofrequency fields in a controlled, shielded environment. Exposure levels were set to reflect realistic upper environmental values (2 V/m at the head and 1 V/m at the torso). Throughout pre-exposure, exposure, and post-exposure phases, HRV was continuously measured under resting eyes-open and eyes-closed conditions. Analysis revealed no statistically significant differences across time- or frequency-domain HRV parameters between real and sham exposures at any phase of exposure. These data suggest that short-term exposure to 26 GHz millimeter waves at environmentally relevant intensities does not alter cardiac autonomic regulation in resting healthy adults. This aligns with the known limited tissue penetration of millimeter waves and the absence of clearly identified biological mechanisms affecting deeper autonomic control at these frequencies. Still, as the exposure duration was relatively brief and the population limited to healthy young individuals, further studies are needed to investigate longer exposures, potential effects during autonomic modulation such as orthostatic maneuvers, and responses in more diverse or vulnerable groups. However, these findings contribute valuable information indicating that no measurable acute physiological changes were observed under the specific environmental exposure conditions investigated; these findings do not address possible long-term or cumulative effects.