| Subject: Re: Closed Field Experiments |
Author:
J Rubin
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Date Posted: 10:43:08 05/27/06 Sat
In reply to:
James Rubin
's message, "Closed Field Experiments" on 10:40:54 05/27/06 Sat
Here is the other study:
Are some people sensitive to mobile phone signals?Within
participants double blind randomised provocation study
G James Rubin,Gareth Hahn,Brian S Everitt,Anthony J Cleare,Simon Wessely
Abstract
Objective To test whether people who report being sensitive to
mobile phone signals have more symptoms when exposed to a
pulsing mobile signal than when exposed to a sham signal or a
non-pulsing signal.
Design Double blind,randomised,within participants
provocation study.
Setting Dedicated suite of offices at King ’s College London,
between September 2003 and June 2005.
Participants 60 “sensitive ”people who reported often getting
headache-like symptoms within 20 minutes of using a global
system for mobile communication (GSM)mobile phone and 60
“control ”participants who did not report any such symptoms.
Intervention Participants were exposed to three conditions:a
900 MHz GSM mobile phone signal,a non-pulsing carrier wave
signal,and a sham condition with no signal present.Each
exposure lasted for 50 minutes.
Main outcome measures The principal outcome measure was
headache severity assessed with a 0-100 visual analogue scale.
Other outcomes included six other subjective symptoms and
participants ’ability to judge whether a signal was present.
Results Headache severity increased during exposure and
decreased immediately afterwards.However,no strong evidence
was found of any difference between the conditions in terms of
symptom severity.Nor did evidence of any differential effect of
condition between the two groups exist.The proportion of
sensitive participants who believed a signal was present during
GSM exposure (60%)was similar to the proportion who
believed one was present during sham exposure (63%).
Conclusions No evidence was found to indicate that people
with self reported sensitivity to mobile phone signals are able to
detect such signals or that they react to them with increased
symptom severity.As sham exposure was sufficient to trigger
severe symptoms in some participants,psychological factors
may have an important role in causing this condition.
Trial registration ISRCTN81432775.
Introduction
The recent uptake of mobile phones has been accompanied by
some concern about possible health risks.
1
In the general popu-
lation,the health effects most often attributed to mobile phone
use are non-specific symptoms.Excluding sensations of mild
warmth,the most commonly reported symptoms are headache,
burning,dizziness,fatigue,and tingling.
2
Mechanisms to explain
these phenomena remain speculative,and although the pulsing
nature of “global system for mobile communication ”(GSM)sig-
nals has been suggested to be partly to blame,
3
experiments that
have exposed healthy adults to GSM signals under blind condi-
tions have not found any significant effects on the reporting of
symptoms.
4
Whether a subgroup of people who are more sensitive to
GSM exists remains unclear.Of particular interest are people
who report symptoms almost every time they use a mobile
phone.
5
This phenomenon falls within the broader category of
“electromagnetic sensitivity,”a medically unexplained condition
in which non-specific symptoms are reported after perceived
exposure to any of a wide range of electrical devices,including
mobile phones,visual display units,and power lines.The preva-
lence of self reported electromagnetic sensitivity in the United
Kingdom is unknown,but community studies in Sweden and
California put the figure at between 1.5%and 3%.
67
Provocation
studies that have exposed people who report electromagnetic
sensitivity to electromagnetic fields under blind conditions have
so far failed to provide any good evidence linking the presence
of electromagnetic fields to severity of symptoms.
8
Several
authors have therefore suggested that psychological mecha-
nisms may be more relevant in causing the condition.
9
We tested whether people with self reported sensitivity to
GSM would experience greater headache severity after double
blind exposure to a GSM signal than after exposure to a sham
signal.Secondary outcomes included other symptoms and abil-
ity to discriminate GSM from sham signals.We also tested
whether a pulsing signal resulted in greater reporting of
symptoms than a non-pulsing signal.
Methods
Study design
In this within participants study,we exposed people who
reported adverse reactions to mobile phone signals (sensitive
group)or who did not report any such effects (control group)to
three conditions:a signal mimicking that produced by a 900
MHz GSM mobile phone,an unpulsed continuous wave signal,
and a sham exposure with no signal present.Our Clinical Trials
Unit determined the order in which these conditions occurred
for each participant on enrolment,by using a computerised ran-
dom numbers generator and counter-balancing within blocks of
six consecutive participants.
Exposures were double blind —that is,neither participants
nor researchers were told which type of exposure was present in
which testing session.The controls for our exposure equipment
allowed for 256 possible settings,of which 15 had been
randomly allocated to each condition.Only the Clinical Trials
Unit knew which settings related to which exposure.For the first
nine control participants and six sensitive participants (11.5%of
all participants),Clinical Trials Unit staff told researchers which
BMJ Online First bmj.com page 1of6
Copyright 2006 BMJ Publishing Group Ltd
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