Medical/biological study (experimental study)

Nocturnal magnetic field exposure: gender-specific effects on heart rate variability and sleep med./bio.

By: Graham C, Sastre A, Cook MR, Gerkovich MM

Published in: Clin Neurophysiol 2000; 111 (11): 1936-1941

Aim of study (acc. to author)

To determine if controlled exposure to magnetic fields alters the heart rate variability and sleep in older (40-60 years) probands.

Background/further details

Healthy men (n=22) and women (n=24) slept in the test room from 23:00 to 07:00 h on two nights spaced over a week. These first two sessions were used to evaluate the effects of nocturnal exposure on cardiac endpoints. Half the subjects selected at random were exposed on the first test night, and then sham exposed on the second night; the remaining subjects participated in the reverse order. One week later, the probands returned for a further two nights to test the sleep parameters.

Endpoint

effects on the cardiovascular system: heart rate, heart rate variability
sleep: sleep pattern

Exposure

- 50/60 Hz
- magnetic field

Exposure	Parameters
Exposure 1: 60 Hz Exposure duration: intermittent for 8 h (1 h on, 1 h off; during field on: field cycled between on and off in 15 s intervals)	magnetic flux density: 28.3 µT

Exposure 1

Main characteristics

Frequency	60 Hz
Type	magnetic field
Waveform	sinusoidal
Polarization	circular
Exposure duration	intermittent for 8 h (1 h on, 1 h off; during field on: field cycled between on and off in 15 s intervals)

Exposure setup

Exposure source	Merritt coils
Chamber	each subject slept overnight in a sound-attenuated and air-conditioned exposure test room (a cube about 2.4 m on each side)
Setup	Merrit-type horizontal and vertical concentric coil system surrounding the exposure chamber; one axis of the field was phase-shifted 90°
Sham exposure	A sham exposure was conducted.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	28.3 µT	-	-	-	-

Additional parameter details

ambient background magnetic field ≤ 0.2 µT

Reference articles

Graham C et al. (1999): Human sleep in 60 Hz magnetic fields
Doynov P et al. (1999): Test facility for human exposure to AC and DC magnetic fields
Sastre A et al. (1998): Nocturnal exposure to intermittent 60 Hz magnetic fields alters human cardiac rhythm
Graham C et al. (1994): Dose response study of human exposure to 60 Hz electric and magnetic fields
Cook MR et al. (1992): A replication study of human exposure to 60-Hz fields: effects on neurobehavioral measures

Exposed system:

human
whole body

Methods Endpoint/measurement parameters/methodology

effects on the cardiovascular system: heart rate, frequency band of heart rate variability power spectrum (low frequency, high frequency, power ratio (low frequency/high frequency)) (ECG)
sleep: sleep pattern (EEG), eye movement (EOG)

Investigated system:

investigation on living organism

Time of investigation:

before exposure
during exposure

Main outcome of study (acc. to author)

Regarding the heart rate variability, under exposure conditions, male probands showed a decrease in the power spectrum (respective low frequency) over the entire night compared to sham exposure conditions. No field-related effects were found in women.
Regarding the sleep, exposed women showed a decreased percentage of time in REM sleep compared to sham exposed women. Additionally, the total amount of time the women remained asleep and sleep efficiency was reduced compared to the sham exposed women. No field-related effects were found in men.
The authors conclude that gender-specific effects seen in this study in older volunteers, replicate the results of previous studies with younger men and women (Sastre, 1998; Sait, 1999; Graham, 1996).

Study character:

medical/biological study
experimental study
full/main study
randomized, double-blind study, cross-over study

Study funded by

Department of Energy, USA
National Institute of Environmental Health Sciences (NIEHS), North Carolina, USA
Oak Ridge National Laboratory (ORNL), USA

McNamee DA et al. (2011): The response of the human circulatory system to an acute 200-muT, 60-Hz magnetic field exposure
McNamee DA et al. (2010): The cardiovascular response to an acute 1800-microT, 60-Hz magnetic field exposure in humans
Mitsutake G et al. (2004): Does exposure to an artificial ULF magnetic field affect blood pressure, heart rate variability and mood?
Tworoger SS et al. (2004): Effect of a nighttime magnetic field exposure on sleep patterns in young women
Graham C et al. (2000): Exposure to strong ELF magnetic fields does not alter cardiac autonomic control mechanisms
Graham C et al. (2000): Heart rate variability and physiological arousal in men exposed to 60 Hz magnetic fields
Graham C et al. (2000): Cardiac autonomic control mechanisms in power-frequency magnetic fields: a multistudy analysis
Sait ML et al. (1999): A study of heart rate and heart rate variability in human subjects exposed to occupational levels of 50 Hz circularly polarised magnetic fields
Sastre A et al. (1998): Nocturnal exposure to intermittent 60 Hz magnetic fields alters human cardiac rhythm