Nocturnal magnetic field exposure: gender-specific effects on heart rate variability and sleep

Objective: To determine if controlled exposure to power-frequency magnetic fields alters heart rate variability (HRV) and polysomnographic endpoints i n healthy men (II = 22) and women (n = 24), 40-60 years of age. Methods: A randomized, double-blind, crossover design was used. Study endpo ints collected during all-night exposure to 60 Hz magnetic fields at an occ upational intensity (resultant flux density = 28.3 microTesla, muT) were co mpared to similar endpoints obtained under equivalent, counterbalanced, no- exposure (less than or equal to0.2 muT) control conditions. Results: Older men, but not women, exposed to the magnetic fields showed po wer reductions in the LF band of the HRV frequency spectrum, which is assoc iated with sympathetically-mediated blood pressure and thermoregulatory con trol (P < 0.04). Older women, but not men, exposed to the fields showed a p attern of disrupted sleep, with reductions in the duration of REM sleep (P = 0.03), and strong trends for reductions in sleep efficiency (P = 0.06) an d total sleep time (P = 0.06). Conclusions: The gender-specific effects seen here with older volunteers re plicate the results of previous exposure studies with younger men and women . (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.