Medical/biological study (experimental study)

Effect of a nighttime magnetic field exposure on sleep patterns in young women med./bio.

By: Tworoger SS, Davis S, Emerson SS, Mirick DK, Lentz MJ, McTiernan A

Published in: Am J Epidemiol 2004; 160 (3): 224-229

Aim of study (acc. to author)

To determine the effect of a continuous, 60 Hz, nighttime magnetic field exposure on sleep outcomes in young women sleeping at home.

Background/further details

Women were studied during two 5-night measurement periods: 1) exposure (0.41-1.21 µT); 2) sham exposure (ambient magnetic field levels, 0.001-0.50 µT). 19 subjects completed one measurement period and 58 completed both. Subjects were between 20-40 years of age, had regular mentrual cycles, were not taking oral contraceptives, and had not breastfed or been pregnant during the previous year. Both measurement periods started two days after the luteinizing hormone surge of the menstrual cycle.

Endpoint

sleep: different sleep parameters

Exposure

- 50/60 Hz
- magnetic field

Exposure	Parameters
Exposure 1: 60 Hz Exposure duration: continuous for 5 nights	magnetic flux density: 0.001 µT minimum (0.001 µT - 0.5 µT; ambient feld) magnetic flux density: 0.5 µT maximum (ambient field) magnetic flux density: 0.41 µT minimum (0.41 µT - 1.21 µT exposure field) magnetic flux density: 1.21 µT maximum (exposure field)

Exposure 1

Main characteristics

Frequency	60 Hz
Type	magnetic field
Waveform	sinusoidal
Exposure duration	continuous for 5 nights

Exposure setup

Exposure source	electric tooth brush charger underneath the bed
Setup	exposure directed at the center of the pillow
Sham exposure	A sham exposure was conducted.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	0.001 µT	minimum	measured	-	0.001 µT - 0.5 µT; ambient feld
magnetic flux density	0.5 µT	maximum	measured	-	ambient field
magnetic flux density	0.41 µT	minimum	measured	-	0.41 µT - 1.21 µT exposure field
magnetic flux density	1.21 µT	maximum	measured	-	exposure field

Exposed system:

human
partial body: head

Methods Endpoint/measurement parameters/methodology

endocrine changes: pregnanediol-3-glucuronide in urine (during the last night of sleep, enzyme immunoassay)
sleep: motor activity: sleep/wake status, sleep efficiency (total sleep time divided by time in bed; actigraphy); sleep diary (bed time, rise time, medication, alcohol consumption)
height, weight, demographic information (job status, exercise, habits)

Investigated system:

isolated bio./chem. substance
urine samples
investigation on living organism

Time of investigation:

during exposure

Main outcome of study (acc. to author)

During the sham exposure (ambient magnetic field) subjects slept on average 6 hours and 58 minutes, with a sleep efficiency of 88.3 %. During the exposure period they slept on average 7 hours and 1 minute, with a sleep efficiacy of 88.4 %. Sleep outcomes were not significantly different between the exposure and sham exposure.

Study character:

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

Study funded by

National Cancer Institute (NCI; U.S. National Institutes of Health), Maryland, USA
National Institute of Environmental Health Sciences (NIEHS), North Carolina, USA

Monazzam MR et al. (2014): Sleep quality and general health status of employees exposed to extremely low frequency magnetic fields in a petrochemical complex
Barsam T et al. (2012): Effect of extremely low frequency electromagnetic field exposure on sleep quality in high voltage substations
Li CY et al. (2002): Residential exposure to power frequency magnetic field and sleep disorders among women in an urban community of northern Taiwan
Pelka RB et al. (2001): Impulse magnetic-field therapy for insomnia: a double-blind, placebo-controlled study
Graham C et al. (2000): Heart rate variability and physiological arousal in men exposed to 60 Hz magnetic fields
Graham C et al. (2000): Nocturnal magnetic field exposure: gender-specific effects on heart rate variability and sleep
Graham C et al. (1999): Human sleep in 60 Hz magnetic fields
Akerstedt T et al. (1999): A 50-Hz electromagnetic field impairs sleep
Sastre A et al. (1998): Nocturnal exposure to intermittent 60 Hz magnetic fields alters human cardiac rhythm