Feb 2, 2022
My Comments on the International MOBI-Kids Study
In December 2021, almost seven years after data collection
was completed, the main outcome paper for the International MOBI-Kids study was
finally published. This case-control study examined brain tumor risk from
wireless phone use among young people 10-24 years of age (Castaño-Vinyals et al, 2022) (see abstract below).
Conducting a multinational
epidemiologic study involving more than 50 scientists with data collected in 14
nations is a complex endeavor with a substantial risk of failure. Although the investigators
made an exemplary effort to salvage the study via supplemental sub-studies and
post-hoc analyses, after reviewing their paper, we believe they were
unsuccessful in overcoming serious methodological problems. Hence, in our opinion,
the data seem uninterpretable, and the study's results should be dismissed.
The authors of the MOBI-Kids study appear to agree with our assessment
because they concluded in the paper’s abstract:
"Further analyses suggest that
the large number of ORs below 1 in this study is unlikely to represent an
unknown causal preventive effect of Mobile phone exposure: they can be at least
partially explained by differential recall by proxies and prodromal symptoms
affecting phone use before diagnosis of the cases. We cannot rule out, however,
residual confounding from sources we did not measure.
Overall, our study provides no evidence
of a causal association between wireless phone use and brain tumours in young
people. However, the sources of bias summarised above prevent us from ruling
out a small increased risk."
Based upon our
review of the research on brain tumor risk among adults who use mobile
phones (Choi
et al., 2020), we recommend that those who must
use mobile phones should keep their use as low as reasonably achievable (ALARA)
and should follow safety guidelines. These
guidelines especially apply to children and adolescents whose brains and bodies
are still developing.
Specific concerns re: the MOBI-Kids study methodology
We believe there is an explanation
for the many risk estimates less than 1 in the MOBI-Kids study. The study had
substantially lower participation rates for controls (54%) than cases (72%) that
likely biased brain tumor risk estimates downward. The investigators conducted
a non-participation study to estimate the amount of this bias, but this study also
had serious limitations (i.e., small sample sizes; differential participation
rates) and likely underestimated the amount of selection bias in the current paper.
The original study design called for
recruitment of 2,000 cases (Sadetzki
et al., 2014). Due to problems with recruitment, the study managed to enroll only 898 cases. Moreover, the primary analyses in the outcome paper included only 671 cases with neuroepithelial
brain tumors (NBT). Hence, the study had inadequate sensitivity (i.e.,
statistical power) to detect even a moderate-sized effect (let alone a small
effect) from mobile phone use on brain tumor risk.
In a case-control study, controls
should be selected that have equal risk for the study outcome as the cases. We
question whether using youth diagnosed with appendicitis as controls constitutes
a suitable choice for a study of cell phone users. Why didn't the study include
a population-based control group like the INTERPHONE study which preceded it (Cardis et al., 2007)?
During the data collection period (2010-2015),
many young people in this study may have used smart phones. Whereas earlier
cellphones had antennas at the top of the phone, many smart phones have
cellular transmission antennas in the bottom of the phones exposing the neck to
the greatest radio frequency radiation, not the head. This may increase the risk
of other tumors, especially thyroid gland tumors,
but reduce the brain tumor risk.
Finally,
ten or fewer years of mobile phone use may not be a sufficient amount of time
before a mobile phone-related brain tumor is diagnosed
in this young population. However, the CEFALO study (Aydin et al., 2011) of children's mobile
use and brain tumor risk did find a significant dose-response relationship for
the number of years of cellphone use in a subsample of participants with mobile phone operator (i.e. telephone company) data. The MOBI-Kids study also had mobile phone operator
data on 25% of participants but did not report the outcome results for this subsample.
MOBI-Kids and CEFALO differed in
important ways. MOBI-Kids used hospital controls whereas CEFALO selected controls
from the general population. Whereas MOBI-Kids included only neuroepithelial brain tumors (NBT) in its primary analyses,
CEFALO did not exclude any brain tumors. MOBI-Kids collected data years later when
different cellular technology was popular, and mobile phone towers likely were
located more proximal to users which may have resulted in less exposure to RFR
emitted by cellphones. Although MOBI-Kids collected data in 14 countries, most of
the data were from five countries, Spain, Italy, France, Israel, and Germany,
and none was from the four CEFALO countries, Denmark, Norway, Sweden, and Switzerland.
In sum, it is unfortunate
that after such a major investment of resources and time that little can be
learned from the MOBI-Kids study about the risk of brain tumors from wireless
phone use in young people. Since the study addresses an issue critical to public health and the majority of the funding was from the European Commission, the MOBI-Kids data set
should be made available to the scientific community for secondary analysis to enable
the data to be re-analyzed using different assumptions and methods.
--
Wireless phone use in childhood and adolescence and neuroepithelial
brain tumours: Results from the international MOBI-Kids study
Castaño-Vinyals G, Sadetzki S, Vermeulen R,
Momoli F, Kundi M, Merletti F, Maslanyj M, Calderon C, Wiart J, Lee AK, Taki M,
Sim M, Armstrong B, Benke G, Schattner R, Hutter HP, Krewski D, Mohipp C, Ritvo
P, Spinelli J, Lacour B, Remen T, Radon K, Weinmann T, Petridou ET, Moschovi M,
Pourtsidis A, Oikonomou K, Kanavidis P, Bouka E, Dikshit R, Nagrani R, Chetrit
A, Bruchim R, Maule M, Migliore E, Filippini G, Miligi L, Mattioli S,
Kojimahara N, Yamaguchi N, Ha M, Choi K, Kromhout H, Goedhart G, 't Mannetje A,
Eng A, Langer CE, Alguacil J, Aragonés N, Morales-Suárez-Varela M, Badia F,
Albert A, Carretero G, Cardis E. Wireless phone use in childhood and
adolescence and neuroepithelial brain tumours: Results from the international MOBI-Kids
study. Environ Int. 2021 Dec 30;160:107069. doi: 10.1016/j.envint.2021.
Abstract
In recent decades, the
possibility that use of mobile communicating devices, particularly wireless (mobile
and cordless) phones, may increase brain tumour risk, has been a concern,
particularly given the considerable increase in their use by young people. MOBI-Kids,
a 14-country (Australia, Austria, Canada, France, Germany, Greece, India,
Israel, Italy, Japan, Korea, the Netherlands, New Zealand, Spain) case-control
study, was conducted to evaluate whether wireless phone use (and particularly
resulting exposure to radiofrequency (RF) and extremely low frequency (ELF)
electromagnetic fields (EMF)) increases risk of brain tumours in young people.
Between 2010 and 2015, the study recruited 899 people with brain tumours aged
10 to 24 years old and 1,910 controls (operated for appendicitis) matched to
the cases on date of diagnosis, study region and age. Participation rates were
72% for cases and 54% for controls. The mean ages of cases and controls were
16.5 and 16.6 years, respectively; 57% were males. The vast majority of study
participants were wireless phones users, even in the youngest age group, and
the study included substantial numbers of long-term (over 10 years) users: 22%
overall, 51% in the 20-24-year-olds. Most tumours were of the neuroepithelial
type (NBT; n = 671), mainly glioma. The odds ratios (OR) of NBT appeared to
decrease with increasing time since start of use of wireless phones, cumulative
number of calls and cumulative call time, particularly in the 15-19 years old
age group. A decreasing trend in ORs was also observed with increasing
estimated cumulative RF specific energy and ELF induced current density at the
location of the tumour. Further analyses suggest that the large number of ORs
below 1 in this study is unlikely to represent an unknown causal preventive
effect of mobile phone exposure: they can be at least partially explained by
differential recall by proxies and prodromal symptoms affecting phone use
before diagnosis of the cases. We cannot rule out, however, residual
confounding from sources we did not measure. Overall, our study provides no
evidence of a causal association between wireless phone use and brain tumours
in young people. However, the sources of bias summarised above prevent us from
ruling out a small increased risk.
Highlights
• Increasing use of mobile technologies by young people is a
topic of public health concern.
• MOBI-Kids studied brain tumour risk and wireless phone use
(and EMF) in 14 countries.
• The study includes 899 brain tumour cases aged
10–24 years old and 1,910 controls.
• We have no evidence of a causal association between wireless
phone use and brain tumours.
• Because of likely biases we cannot rule out a small increased
risk.
Open access paper: https://www.sciencedirect.com/science/article/pii/S0160412021006942?via%3Dihub
