Study type: Medical/biological study (experimental study, observational study)

Effect of short-wave (6-22 MHz) magnetic fields on sleep quality and melatonin cycle in humans: the Schwarzenburg shut-down study. med./bio.

Published in: Bioelectromagnetics 2006; 27 (2): 142-150

Aim of study (acc. to author)

This study describes the results of a unique "natural experiment" of the operation and cessation of a broadcast transmitter with its short wave electromagnetic fields (6-22 MHz) on sleep quality and melatonin cycle in a general human population sample.

Background/further details

In 1998, 54 volunteers were followed for one week each before and after shut-down of the short wave radio transmitter at Schwarzenburg (Switzerland).
Melatonin was sampled five times a day. Sleep quality was recorded daily.



Exposure Parameters
Exposure 1: 6.1–21.8 MHz
Modulation type: AM
Exposure duration: continuous, studied for 4 days before shutdown

Exposure 1

Main characteristics
Frequency 6.1–21.8 MHz
Exposure duration continuous, studied for 4 days before shutdown
Additional info reference article: Altpeter et al. 1995. Study on health effects of the shortwave transmitter station of Schwarzenburg, Berne, Switzerland. BEW (Bundesamt of Energiewirtschaft); 1995. BEW Publication Series No. 55.
Modulation type AM
Exposure setup
Exposure source
Setup The shortwave transmitter operated with a maximum power of two times 150 kW. The direction of the transmission beam changed about every 2 h according to the local time in the target areas (America, Asia, Africa, Australia). The beam was elevated by 11° above the horizontal.
Measurand Value Type Method Mass Remarks
magnetic field strength 0.4 mA/m mean calculated - median = 0.40 mA/m, low exposure group
magnetic field strength 2.6 mA/m mean calculated - median = 2.1 mA/m, high exposure group

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Investigated organ system:
Time of investigation:
  • during exposure
  • after exposure

Main outcome of study (acc. to author)

During operation of the transmitter self-rated morning freshness as an indicator of sleep quality decreased with increasing exposure to short-wave electromagnetic fields. The authors revealed that sleep quality improved after the transmitter shut-down, and they found evidence suggestive of a rebound in nightly melatonin excretion in poor sleepers. The authors did not find any acute or chronic effects of exposure on the acrophase (peak time of melatonin excretion) of the melatonin cycle.
Due to the observational nature of the study, a direct biological cannot, however, have been causality proven, and the possibility of a psychological rather than a biological effect cannot be excluded. From a public health perspective these results call for caution in exposing populations to electromagnetic fields from short wave radio transmitters.

Study character:

Study funded by

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