Changes in heart rate variability among RF plastic sealer operators

In a previous study, we showed that operators of radiofrequency (RF) plastic sealers, RF operators ( n  = 35) had a lower heart rate during nighttime compared to a control group ( n  = 37). We have analyzed the heart rate variability (HRV) on the same group of people to better understand the possible underlying rhythm disturbances. We found a significantly increased total HRV and very low frequency (VLF) power during nighttime among the RF operators compared to a control group. Together with our previous finding of a significantly lower heart rate during nighttime among the RF operators compared to the controls, this finding indicates a relative increase in parasympathetic cardiac modulation in RF operators. This could in turn be due to an adaptation of the thermoregulatory system and the cardiac autonomic modulation to a long‐term low‐level thermal exposure in the RF operators. Bioelectromagnetics © 2006 Wiley‐Liss, Inc.