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ISIS Report 22/06/11
Wireless Phones and Brain Cancer
Cordless phones similar to mobile phones
for increased risks to brain tumours, especially for the young, where the risks
are five times for users compared with controls Dr. Mae-Wan Ho
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Latest evidence from Sweden confirms risks of wireless phones
Lennart Hardell’s group at University
hospital, Orebro, Sweden, have been investigating the brain cancer risks of
mobile phones since the late 1990s, and conducted several case-control studies
in which cancer cases were compared with matched controls in terms of exposure
to microwaves from mobile phones and more recently, also cordless phones. The
group has consistently found that wireless phones increase the risks of brain
tumours, both malignant and benign, especially on the side of the head where
the mobile phone is used.
The most
persuasive results came from two large case-control studies on brain tumours
assessing the use of mobile phones and cordless phones. These were done by a
standardized questionnaire mailed out to people, and answered in total by 905
(90 percent) of cases with malignant brain tumours, 1 254 (88 percent) cases
with benign tumours and 2 162 (89 percent) population-based matched controls. A
pooled analysis of the data from these two studies confirmed the association of
mobile and cordless phone use with brain tumours.
The highest risk
for both malignant and benign brain tumours was found for the same side of the
head of those who have used wireless phones for more than 10 years.
Significantly, the risks are several times greater for the youngest group: people
who started to use mobile phones when they are less than 20 years old.
Sweden
one of the earliest countries to use mobile phones
Sweden was one of the first countries in the world to adopt mobile phones,
starting with the analogue phones in the early 1980s. From 1981 to the end of
2007, NMT (Norway Mobile Telephone) 450 MHz phones were used; and NMT 900CMHz operated during 1986-2000. The
digital GSM (Global System for Mobile Communication) from 1991 operated with a
dual band of 900 and 1 800 MHz. The third generation of mobile phones, 3G or
UMTS (Universal Mobile Telecommunication System) using 1 900 MHz was introduced
worldwide a few years ago, in Sweden in 2003. The fourth generation (4G) system
is now in the planning stage.
The
desktop cordless phones DECT (Digital Enhanced Cordless Telecommunication) have
been used in Sweden since 1988, at first operating on analogue 800-900 MHz, but
since the early 1990s, the digital 1 900 MHz system is used.
Most
studies on the association between the use of wireless phones and brain tumours
are hampered by insufficient years of use, as the latency period of cancer is
long in comparison. As Sweden was one of the first countries to adopt the
technology, it offers the best opportunity for finding an early association. So
far, the main results are from the Hardell group and from the Interphone study
group. Interphone is a research programme set up in
2000 involving 13 countries to investigate the association between mobile phone
use and cancer risk, particularly brain, head or neck, and coordinated by the
international Agency for Research on Cancer (IARC), part of the World Health
Organisation [2].
Case-control
studies
The Hardell
group carried out 3 case control studies, all by mailed questionnaires. The
first study covered the period 1994-1996, and included 209 cases (90 percent)
and 425 controls (91 percent) that answered the questionnaire. This was
followed by two larger studies using the same methods, over the time period
1997-2003. These studies included cordless phones and more questions on, for
example, occupational exposures. The information was supplemented over the
phone when necessary. The side of the head that had been most used during phone
calls was assessed by separate questions: >50 percent of the time for one
side, or equally both sides. This information was checked during the
supplementary phone calls. Tumour localisation was based on information in medical
records and all tumour types were defined using histopathology reports. The use
of the wireless phone was defined as ipsilateral (tumour on the same side as
phone use >50 percent of the time) and contralateral (<50 percent). From
information on the time period of use and average number of minutes per day
during that period, the latency time (to tumour development), and cumulative
use in hours over the years were calculated. Use in a car with external antenna
was disregarded as well as use of a hands free set. The minimum latency period
for tumours was set at one year. Only living subjects were included in the
studies.
Earlier, I reported the results of the second case-control studies
from the Hardell group, which covered the period 1 January 1997 to 10 June
2000, in [3] (Cordless
Phones and Malignant Brain Tumours, SiS 37); and pointed out then that
the base stations of cordless phones, being in the house, typically expose
residents to much higher intensities of microwaves than any mobile phone
transmitters nearby.
A
third case-control study was carried out using an identical questionnaire to
the second, and covered the period 1 July 2000 to 31 December 2003. In total
729 cases (89 percent) and 692 controls (91 percent) participated.
Analysis of
pooled data
Analysis of the
pooled case studies (2 and 3) clearly showed increased risks of both malignant
astrocytomas as well as benign brain tumours, especially on the same side of the
head the phone is used more than 50 percent of the time. Table 1 summarises the
results on malignant tumours.
Table 1
Odds ratio (OR) and 95% confidence intervals (CI) for malignant tumours in
pooled case control studies 1997-2003
Ca/Co indicate
number of exposed cases and controls respectively
For
astrocytoma, mobile phone use for more than a year (>1 year latency) yields
an odds ratio of 1.4 overall, i.e., users of mobile phones for more than a year
are 1.4 times as likely to get malignant astrocytoma as unexposed controls.
This relative risk increased to 2.0 for the ipsilateral case, the same side of
the head the phone is used. For those who have used mobile phones for more than
10 years (>10 year latency), the risk increased further to 2.7 overall, and
3.3 in the ipsilateral case. For cordless phone users of more than 1 year, the
overall OR is 1.4, and 1.8 for the ipsilateral case. For cordless phone users
of more than 10 years, OR increases to 2.5 overall, and 5.0 for the ipsilateral
case. Other malignant tumours followed the same trends in mobile phone users;
but in cordless phone users the OR for ipsilateral case is smaller than the
contralateral, a deviation probably resulting from the small number of cases.
Similar
trends are found for benign tumours such as acoustic neuroma, meningioma and
other brain tumours, for both mobile and cordless phone users.
The
trends are more pronounced for young users of mobile and cordless phones as can
be seen when the data are separated by age groups (see Table 2). The group that
starts to use mobile and cordless phones before 20 has an OR of 5.2 and 4.4
respectively for malignant astrocytoma after one year (<20, 1 year latency)
compared with 1.4 for both over all ages. This highlights the special
susceptibility of the young to MW radiation from the wireless phones.
Table 2
Odds ratio (OR) and 955 confidence interval (CI) for astrocytoma and acoustic
neuroma in different age groups
Ca/Co indicate
number of exposed cases and controls respectively
Methodological
problems with the Interphone study
Hardell’s group
also analysed the data from the Interphone study [4], a research programme
involving 13 countries set up in 2000 to investigate the association between
mobile phone use and cancer risk, particularly brain, head or neck. The
Interphone study used rather different methods; for example Interphone did not
study cordless phone use, and instead of a standardized questionnaire, a
computer guided personal interview was used for both cases and controls, in which
the interviewer knew in advance whether it was a case or a control. Instead of
drawing cases from the cancer registry, the Interphone study used hospital
records, While the controls in Hardell’s studies were unexposed, i.e., consist
of people who do not use mobile or cordless phones at all, or have used them
for less than one year, the Interphone study unexposed group include those who
have used cordless phones. Similarly, while the Hardell studies included as
exposed cases people who have used mobile or cordless phones at any time, the
Interphone study defined mobile phone use as ‘regular use´ on average once per
week during at least 6 months; less than that was regarded as unexposed. The
response rates for both cases and controls were substantially lower in the
Interphone study. For these and other reasons, the Interphone study suffers
from many weaknesses, as pointed out by Hardell [1], who suggested that the
observations were biased and hence unreliable.
Indeed, an article published [5] by two participants (one of them
the coordinator) of the Interphone study reviewed both the Hardell and
Interphone results and concluded that overall, the findings suggest “the
existence of possible association” between mobile phone use and head cancers,
and recommended simple and low cost measures to reduce exposures as a
precaution particularly among young people.
In a more recent publication, the Hardell group presented a further
pooled analysis of case-control studies on malignant brain tumours and the use
of mobile and cordless phones that included both living and deceased subjects,
and the same results were found [6]. The risks of brain tumours go up with
latency time (years of use) and cumulative use in hours, and are highest in
subjects using mobile or cordless phones before the age of 20.
References
1.
Hardell L. Wireless phone use and brain tumour
risk. In Giuliani L and Soffritti M. eds. Non-thermal Effects and Mechanisms
of Interaction between electromagnetic Fields and Living Matter, an ICEMS
Monograph, Ramazzini Institute, European Journal of Oncology Library vol.5, pp.
363-78, Bologna, Italy, 2010.
2.
The Interphone Study, Health Protection Agency,
topics, accessed 7 May 2011, http://www.hpa.org.uk/Topics/Radiation/UnderstandingRadiation/UnderstandingRadiationTopics/
ElectromagneticFields/MobilePhones/info_INTERPHONE/
3.
Ho MW. Cordless phones & malignant brain
tumours. Science in
Society 37, 18-19, 2008.
4.
The Interphone Study, Health Protection Agency,
topics, accessed 7 May 2011, http://www.hpa.org.uk/Topics/Radiation/UnderstandingRadiation/UnderstandingRadiationTopics/
ElectromagneticFields/MobilePhones/info_INTERPHONE/
5.
Cardis E and Sadetzki S. Indications of possible
brain tumour risk in mobile phone studies: should we be concerned? Occup Environ Med 2011, 68, 169-71.
6.
Hardell L, Carlberg M and Mild KH. Pooled
analysis of case-control studies on malignant brain tumours and the use of
mobile and cordless phones including living and deceased subjects. International
Journal of Oncology 2011, 38, 1465-74.
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