Neurophysiological study of patients with perceived ‘electrical hypersensitivity’

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Abstract

The aim of the present study was to investigate baseline neurophysiological characteristics of the central and autonomous regulation and their reactivity to different tests in a group of persons with so-called ‘electrical hypersensitivity’, which is often considered as a form of psychosomatic disorders. Twenty patients with combinations of neuroasthenic symptoms (general fatigue, weakness, dizziness, headache) and facial skin (itching, tingling, redness) have been investigated. An equal number of symptom-free persons served as a control group. The examination comprised self-reported measures, testing of visual functions, measurements of blood pressure, heart rate and its variability, electrodermal activity, respiration, EEG and visual evoked potentials (VEP). Several variables were found to differ between the patient and the control groups. The mean value of heart rate in rest condition was higher in the patient group compared to the controls (mean value of inter-beat intervals were 0.80 and 0.90 s, respectively). Heart rate variability and response to standing test were decreased in the patient group compared to the controls. Patients had faster onset, higher amplitudes, and left-right hand asymmetry of the sympathetic skin responses. They had a higher critical fusion frequency (43 vs. 40 Hz), and a trend to increased amplitude of steady-state VEPs at stimulation frequencies of 30–70 Hz. The data indicated that the observed group of patients had a trend to hyper sympathotone, hyperresponsiveness to sensor stimulation and heightened arousal.

Introduction

‘Electrical hypersensitivity’ (EHS) is a term used to describe persons who subjectively associate their non-specific symptoms with electric and/or magnetic field exposure. The problem arose in the beginning of 1980s when a number of office workers reported an association of their health problems with the use of video display units. Psychosocial factors at the workplace, lighting as well as electromagnetic fields (EMF) emitted from the computer displays have been discussed in this context. Later, discussions have focused on the role of EMF in the genesis of this form of environmental maladaptation since many persons also associated their symptoms to exposure to other electrical equipment (Knave et al., 1985, Berg et al., 1993).

The clinical pattern of EHS typically includes neuroasthenic and vegetative symptoms such as fatigue, tiredness, concentration difficulties, dizziness, nausea, heart palpitation and digestive disturbances as well as facial skin symptoms, such as redness, tingling and burning sensations (Bergdahl et al., 1994, Arnetz and Berg, 1996). It should be noted that the use of the term ‘electrical hypersensitivity’ does not imply an already established causal relationship between EMF and the symptoms. Results of provocation studies have not shown any distinctive physiological reactions or subjective sensation in response to laboratory exposure to various electric and/or magnetic fields (Bergqvist et al., 1997).

The lack of correlation between EMF exposure and appearance and severity of symptoms led to a discussion of a primarily psychosomatisation mechanism behind the electrical hypersensitivity and its common origin with other forms of environmental intolerance like multiple chemical sensitivity and other functional syndromes (Lidén, 1996, Göthe et al., 1995, Berg et al., 1992). It is assumed that different forms of environmental intolerance all involve the same pathophysiologic disregulation mechanism, and decompensated neuroendocrine response to stress (Barsky and Borus, 1999).

A previous study in our laboratory revealed a trend towards high basal values in heart rate, and higher amplitude of visual steady-state evoked potentials in the patient group in comparison with the control group (Sandström et al., 1997). Wang et al. (1994), studied 19 patients with combined chemical and electrical hypersensitivity and showed higher baseline values in blood pressure and heart rate, as well as changes in pupil response to light flashes in the patient group in comparison with control subjects. These preliminary physiological findings might indicate a possible involvement of the autonomous nervous system and a hyperresponsiveness to sensor stimulation (e.g. amplitude modulated light) in persons with perceived EHS. Such a pattern of physiological deviations have been discussed as a possible common background for several stress-related and psychosomatic disorders (Giardino and Lehrer, 2000). This can lead to an increased vulnerability to a variety of psychological and physical stressors.

Therefore, the aim of the present study was to investigate the baseline neurophysiological characteristics of the central and autonomous regulation, and their reactivity to various functional tests in a group of EHS patients in comparison with a control group.

Section snippets

Subjects

Twenty patients (11 female, 9 male, mean age 47±5 years) with symptoms they associated with exposure to EMF have been selected for the present study from the Departments of Occupational Medicine and Dermatology at the Norrland University Hospital, Umeå, Sweden. All patients had a combined pattern of skin, general and ocular symptoms. The duration of experienced symptoms varied from 1 to 10 years. The most frequent symptoms in the group were tingling of the facial and neck skin (13 cases), skin

Results

Self ratings of subjective complaints before examination was almost at ‘zero’ level in the control group, and moderate (not exceeding 4 of 10 maximum scores for any symptom) in the patient group. Patients commonly complained of weak or moderate skin redness, tingling and itching, as well as fatigue and dizziness. Nine patients and two subjects from the control group noted a small increase in symptoms after the examination (within 2 scores, not exceeding 5 scores maximum). No subjects showed

Discussion

The character of the symptoms in the patient group coincided well with data obtained in other surveys (Bergqvist and Wahlberg, 1994, Hillert and Kolmodin-Hedman, 1997). A combination of general non-specific (general fatigue, weakness, dizziness, headache) and skin (facial itching, tingling, redness) symptoms were most typical for the patients. Anamnesis and results of the self-assessment rate showed recurrent and rather moderate levels of symptoms in the patient group.

Accumulated experience of

Acknowledgements

We thank Drs Berndt Stenberg, Lars Widman and Håkan Linderholm1, (Norrlands University Hospital), and Dr Ole Marqvardsen (Sundsvalls Hospital), for their help in examining and recruiting patients for this study. Our special thanks to Prof. Yu. Shelepin (Institute of Physiology, RAN) for kindly presenting a set of visuocontrast tables. We also thank the members of our staff who helped make the study possible: Nils

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