Two cross-sectional studies and two panel studies were conducted in the area of Schwarzenburg, Switzerland. In each cross-sectional study, about 400 adults living in different distances to the transmitter were asked about somatic and psycho-vegetative symptoms including sleep disturbances. In the panel studies, melatonin excretion of 65 and 54 persons was measured and sleep quality was assessed by a diary to compare the period before and after shut-down of the transmitter.
|Reference group 1||zone C: 3000 - 5000 m from the transmitter, 1 - 2 mA/m, median 1 mA/m: unexposed|
|Group 2||zone A: up to 900 m from the transmitter, 14 - 41 mA/m, median 28 mA/m: exposed|
|Group 3||zone C: 900 - 1500 m from the transmitter, 3 - 37 mA/m, median 21mA/m: exposed|
|Group 4||zone R: Rueggisberg, ≤ 10 mA/m: exposed|
The prevalence of difficulties of falling asleep and maintaining sleep increased with increasing radiofrequency electromagnetic field exposure in both cross-sectional studies. Sleep quality improved after transmitter shut-down. No chronic change of melatonin excretion was observed.
The authors concluded that the results of the studies give strong evidence of a causal relationship between the operation of a short-wave broadcast transmitter and sleep disturbances in the surrounding population, but there is insufficient evidence to distinguish between a biological and psychological effect.