Magnetic fields exposure from high-voltage power lines and risk of amyotrophic lateral sclerosis in two Italian populations

Abstract

The aetiology of amyotrophic lateral sclerosis (ALS), a rare and extremely severe neurodegenerative disease, has been associated with magnetic fields exposure. However, evidence for such a relation in the general population is weak, although the previous null results might also be due to exposure misclassification, or a relationship might exist only for selected subgroups. To test such a hypothesis we carried out a population-based case-control study in two Northern and Southern Italy regions, including 703 ALS cases newly diagnosed from 1998 to 2011 and 2737 controls randomly selected from the residents in the study provinces. Overall, we found that a residence near high-voltage power lines, within the corridors yielding a magnetic fields of ≥0.1 μT, was not associated with an excess disease risk, nor did we identify a dose-response relationship after splitting the exposed corridor according to the 0.1, 0.2 and 0.4 μT cut-points of exposure. These results were confirmed taking into account age at onset, period of diagnosis, sex, geographical area, and length of exposure. Overall, despite the residual possibility of unmeasured confounding or small susceptible subgroups not identified in our study, these results appear to confirm that the exposure to magnetic fields from power lines occurring in the general population is not associated with increased ALS risk.

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Amyotrophic Lateral Sclerosis and Frontotemporal
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Magnetic fields exposure from high-voltage power
lines and risk of amyotrophic lateral sclerosis in
two Italian populations
Marco Vinceti , Carlotta Malagoli, Sara Fabbi, Leeka Kheifets, Federica
Violi, Maurizio Poli, Salvatore Caldara, Daniela Sesti, Silvia Violanti,
Paolo Zanichelli, Barbara Notari, Roberto Fava, Alessia Arena, Roberta
Calzolari, Tommaso Filippini , Laura Iacuzio, Elisa Arcolin, Jessica Mandrioli,
Nicola Fini, Anna Odone, Carlo Signorelli, Francesco Patti, Mario Zappia,
Vladimiro Pietrini, Paola Oleari, Sergio Teggi, Grazia Ghermandi, Angela
Dimartino, Caterina Ledda, Cristina Mauceri, Salvatore Sciacca, Maria Fiore
& Margherita Ferrante
To cite this article: Marco Vinceti , Carlotta Malagoli, Sara Fabbi, Leeka Kheifets, Federica
Violi, Maurizio Poli, Salvatore Caldara, Daniela Sesti, Silvia Violanti, Paolo Zanichelli, Barbara
Notari, Roberto Fava, Alessia Arena, Roberta Calzolari, Tommaso Filippini , Laura Iacuzio, Elisa
Arcolin, Jessica Mandrioli, Nicola Fini, Anna Odone, Carlo Signorelli, Francesco Patti, Mario
Zappia, Vladimiro Pietrini, Paola Oleari, Sergio Teggi, Grazia Ghermandi, Angela Dimartino,
Caterina Ledda, Cristina Mauceri, Salvatore Sciacca, Maria Fiore & Margherita Ferrante (2017):
Magnetic fields exposure from high-voltage power lines and risk of amyotrophic lateral sclerosis
in two Italian populations, Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration, DOI:
10.1080/21678421.2017.1332078
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Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration, 2017; 1–7
RESEARCH ARTICLE
Magnetic fields exposure from high-voltage power lines and risk of
amyotrophic lateral sclerosis in two Italian populations
MARCO VINCETI
1,2
, CARLOTTA MALAGOLI
1
, SARA FABBI
3
, LEEKA KHEIFETS
4
,
FEDERICA VIOLI
1
, MAURIZIO POLI
5
, SALVATORE CALDARA
6
, DANIELA SESTI
5
,
SILVIA VIOLANTI
5
, PAOLO ZANICHELLI
5
, BARBARA NOTARI
5
, ROBERTO FAVA
5
,
ALESSIA ARENA
6
, ROBERTA CALZOLARI
6
, TOMMASO FILIPPINI
1
,
LAURA IACUZIO
1
, ELISA ARCOLIN
1
, JESSICA MANDRIOLI
7
, NICOLA FINI
7
,
ANNA ODONE
8
, CARLO SIGNORELLI
8,9
, FRANCESCO PATTI
10
, MARIO ZAPPIA
10
,
VLADIMIRO PIETRINI
11
, PAOLA OLEARI
12
, SERGIO TEGGI
3
, GRAZIA GHERMANDI
3
,
ANGELA DIMARTINO
10
, CATERINA LEDDA
10
, CRISTINA MAUCERI
10
,
SALVATORE SCIACCA
10
, MARIA FIORE
10
& MARGHERITA FERRANTE
10
1
Environmental, Genetic, and Nutritional Epidemiology Research Center - CREAGEN, Department of Biomedical,
Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy,
2
Department of
Epidemiology, Boston University School of Public Health, Boston, MA, USA,
3
Department of Engineering ‘‘Enzo
Ferrari’’, University of Modena and Reggio Emilia, Modena, Italy,
4
Department of Epidemiology, UCLA Fielding
School of Public Health, Los Angeles, CA, USA,
5
Emilia-Romagna Regional Agency for Environmental Prevention
and Energy (ARPAE), Emilia-Romagna Region, Italy,
6
Sicilia Regional Agency for Environmental Prevention
(ARPA), Palermo, Italy,
7
Department of Neuroscience, S.Agostino-Estense Hospital, Policlinico University
Hospital, Modena, Italy,
8
Department of Biomedical, Biotechnological, and Translational Sciences, University of
Parma, Parma, Italy,
9
University ‘Vita-Salute’ San Raffaele, Milan, Italy,
10
Department of Medical, Surgical
Sciences and Advanced Technologies ‘‘G.F. Ingrassia’’, University of Catania, Catania, Italy,
11
Department of
Neuroscience, University of Parma, Parma, Italy, and
12
Information and Communication Technology Department,
Local Health Unit of Reggio Emilia and IRCCS-Arcispedale Santa Maria Nuova, Reggio Emilia, Italy
Abstract
The aetiology of amyotrophic lateral sclerosis (ALS), a rare and extremely severe neurodegenerative disease, has been
associated with magnetic fields exposure. However, evidence for such a relation in the general population is weak, although
the previous null results might also be due to exposure misclassification, or a relationship might exist only for selected
subgroups. To test such a hypothesis we carried out a population-based case-control study in two Northern and Southern
Italy regions, including 703 ALS cases newly diagnosed from 1998 to 2011 and 2737 controls randomly selected from the
residents in the study provinces. Overall, we found that a residence near high-voltage power lines, within the corridors
yielding a magnetic fields of !0.1 lT, was not associated with an excess disease risk, nor did we identify a dose-response
relationship after splitting the exposed corridor according to the 0.1, 0.2 and 0.4 lT cut-points of exposure. These results
were confirmed taking into account age at onset, period of diagnosis, sex, geographical area, and length of exposure.
Overall, despite the residual possibility of unmeasured confounding or small susceptible subgroups not identified in our
study, these results appear to confirm that the exposure to magnetic fields from power lines occurring in the general
population is not associated with increased ALS risk.
Keywords: Amyotrophic lateral sclerosis, electromagnetic fields, case-control study, epidemiology, risk, power lines
Correspondence author: Marco Vinceti, Department of Biomedical, Metabolic and Neura l Sciences, University of Modena and Reggio Emilia, Via Campi
287, 41125 Modena, Italy. E-mail: marco.vinceti@unimore.it
(Received 4 February 2017; revised 5 May 2017; accepted 15 May 2017)
ISSN 2167-8421 print/ISSN 2167-9223 online !2017 World Federation of Neurology on behalf of the Research Group on Motor Neuron Diseases
DOI: 10.1080/21678421.2017.1332078

Introduction
Amyotrophic lateral sclerosis (ALS) is a rare
neurodegenerative disorder, characterised by the
progressive degeneration of motor neurons and
leading to extreme disability and death within 3–5
years from disease onset (1,2). During recent
decades, an increased ALS incidence has been
reported in Western countries (3,4), including Italy
(5–9). While substantial advancements in the assess-
ment of genetic factors involved in ALS aetiology
have been made, the role of environmental factors is
still largely unknown (3,10–13). Among the putative
environmental risk factors, including intense phys-
ical activity, trauma, exposure to pesticides, heavy
metals and selenium (12,14–18), the magnetic fields
(MF) in particular have been associated with ALS
in some occupational studies (19–21), although
other studies have failed to detect such an associ-
ation (22–24), suggesting that electrical shocks or
other unidentified factors may induce the excess
disease risk in electricity workers (25). Results of the
four recent studies investigating the role of MF
generated by high-voltage power lines in the general
population have yielded null findings (26–29).
However, these studies have been based on distance
of the residence from power lines, which may be a
poor surrogate of MF exposure and therefore induce
exposure misclassification (30,31). In addition, the
issue of a potential association between MF and
ALS is worth investigating taking into account the
extreme severity of the disease, despite the rather
limited number of people exposed to these fields.
We here report the results of the first population-
based study on this issue based on assessment of MF
exposure from high-voltage power lines, which was
carried out in Italy, a country with rather high
ALS incidence, and included two regions charac-
terised by different environmental and life-style
characteristics.
Methods
Study population
We aimed at retrieving all newly-diagnosed ALS
cases in three provinces of the Emilia-Romagna
region in Northern Italy (Modena, Reggio Emilia
and Parma – around 1,700,000 inhabitants) and in
the Sicilian province of Catania (around 1,100,000
inhabitants) from 1998 to 2011. For this purpose,
and after approval of the Modena and Catania ethics
committees, we used different sources of data, with
a methodology adopted in previous studies (32). We
used the Emilia-Romagna Region ALS Registry
(33,34) to retrieve cases diagnosed in this region
from 2009 (commencement year of the register),
and three databases from the National Health
Service (NHS) to retrieve the cases diagnosed in
the 1998–2008 period: hospital discharge records,
death certificates and drug prescriptions records. In
collaboration with expert neurologists (JM, NF,
VP), we reviewed Emilia Romagna Region hospital
discharges for both inpatients and outpatients of
public and private regional hospitals using code
335.2 of the International Classification of Disease
from 1998 to 2008, death certificates from 1998 to
2008 reporting the above mentioned code, and all
riluzole prescriptions issued between 2001 (the
starting year since when they were available) and
2008. To identify cases of ALS diagnosed in Catania
province residents, we used the hospital discharge
records and the death certificates covering the entire
study period from the Policlinico Hospital and the
Local Health Unit of Catania. These records were
reviewed by two neurologists (FP, MZ) to validate
ALS diagnosis.
Through the Revenue Agency of the Ministry of
Finance and the National Health Services direc-
tories we ascertained the residential address of cases
at the date of diagnosis and of matched controls, as
well as their historical residence since 1979, the
earliest year for which residential information was
available. We georeferenced all addresses using a
methodology described elsewhere (31,35,36), based
on the satellite coordinates retrieved from the
database of the provinces of Modena, Parma,
Reggio Emilia and Catania, and through site meas-
urement with a portable Geographic Positioning
System device (GPSmap 60CSx, Garmin Int.
Corp., Olathe, KS) for unavailable addresses. We
included all these geocoded addresses in a
Geographical Information System (GIS), using
ARC-GIS software (version 10, ESRI, Redlands,
CA 2010).
Exposure assessment
We assessed exposure by modelling MFs exposure at
the subjects’ residence, as previously explained in
detail (31,35). Briefly, we used geodata on the high-
voltage power lines (!132 kV) located during the
1998–2011 period in the study territory as available
at the Emilia-Romagna and Sicily regional agencies
for environmental protection. In this period, there
were 194 lines operating in the study provinces (171
with 132–150 kV, 10 with 220 kV, and 13 with
380 kV), having a total length of 2539 km (579, 546,
701, 713 for Modena, Reggio Emilia, Parma and
Catania, respectively), and all of which had been
already operating since 1998 and 71% since 1979.
Precision of geocoding of these lines was in the order
of 51 m, and its accuracy was tested during the
study with both Google Earth and on-site visit to
determine the accuracy of the available data. We also
had available from our files the code, average
current intensity and voltage for all these lines. We
then calculated MF induction in the proximity of
these lines using the CAMPI model to define the
distance at which, at a height of 8 m, the intensity
2M. Vinceti et al.

cut-points of 0.1, 0.2 and 0.4 microTesla (lT)
occurred. The CAMPI model is a 2D freeware
software simulation package that predicts the mag-
netic flux density generated by high voltage power
lines (37). This model works considering all the
conductors as rectilinear, horizontal, parallel, and
having infinite length. The ground plane and all the
other objects (such as pylons, buildings, trees, etc.)
are considered as transparent to the MF. We
originally validated the model around a high-voltage
power line of the Emilia-Romagna region: this
model performed extremely well in predicting the
measured MF around the line (38). When running
the model for the present study, we took into
account the electrical and geometric characteristics
of each power line (phases and the most frequent
disposition of conductors), and we used the average
current flowing in the power lines during 2001, the
earliest year for which data are available from the
regional environmental protection agencies, already
described elsewhere (31,35). Historical analysis of
current consumption and requirements over the
1986–2007 period according to national electricity
company data indicates that the currents run in
power lines in both the Emilia-Romagna and the
Sicily region increased over time of about 3% on a
yearly basis, with the 2001 values being, respect-
ively, 13.5% and 13.3% higher than the average
values of the whole period. In the present study,
exposure assessment was done blindly to the case
and control status.
Data analysis
We estimated the relative risks of ALS in relation to
MFs exposure from power lines by calculating the
disease odds ratio (OR) and 95% confidence inter-
vals (CI) in crude conditional logistic regression,
both in single exposure strata and after collapsing
the three upper categories into a single one, for
dichotomous analysis. We always used as reference
category 50.1 lT. When no valid estimate could be
computed due to the limited sample size, we used an
unconditional logistic regression model adjusting for
age and sex. We also repeated these analyses with a
multivariate model, including as potential confoun-
ders the year of diagnosis (to take into account small
variations of current in the power lines) and rural
residence (to account for the possible role of
pesticides in disease aetiology (14,39)). For this
purpose we inputted in the model the percentage of
rural area in a circular buffer of a 100 m radius
around the houses, on the basis of a GIS-based
mapping of Italian territory periodically updated by
remote sensing as described elsewhere (40). Finally,
to better detect possible dose-response relations
between MF exposure and ALS risk, we conducted
analyses in subsets of individuals who were residen-
tially stable, i.e. resident in the same place for at
least 20 years before date of inclusion in the study.
Results
We identified 718 eligible cases of ALS diagnosed
during the study period and a corresponding
number of 2872 matched controls. After geocoding,
15 (2.1%) cases and 135 (4.7%) controls could not
be included due to missing or incomplete addresses
or lack of actual residence in the province of interest.
The final database consisted, therefore, of 3440
individuals (703 cases and 2737 controls), 2434 of
whom (499 cases and 1935 controls) located in the
Emilia-Romagna region and 1006 (204 cases and
802 controls) in Sicily. Among these, 994 subjects,
204 (29.0%) cases and 790 (28.9%) controls, were
resident at the same address continuously since the
earliest date we could ascertain, 1979, i.e. at least 20
years. As shown in Table 1, two cases and 11
controls were exposed to MF !0.1 lT (10 (76.9%)
males and three (23.1%) females, mean (standard
deviation) age 66.8 (9.1) and 67.3 (16.3) years,
respectively), whereas 202 cases and 779 controls
(566 (57.7%) males and 415 (42.3%) females, mean
age 68.5 (8.3) and 71.4 (9.7) years, respectively)
were unexposed.
Odds ratio of ALS for people exposed to
MF !0.1 lT compared to50.1 lT was 0.65 (95%
CI 0.27–1.55), based on six exposed cases and 35
exposed controls (Table 2). MF exposure was not
associated with ALS risk both in each of the upper
exposure categories, nor did it show any dose-
response relationship (Table 2). This was confirmed
in multivariate analysis after inputting as covariates
year of ALS onset and vicinity to agricultural areas,
or stratifying the analysis by gender (data not
shown). In addition, breakdown of study population
according to age (cut-point 65 years), period of
disease diagnosis (or inception for matched con-
trols), and study area (Northern and Southern Italy)
did not yield any further indication of a relationship
between MF exposure and ALS risk, with the only
exception being an imprecise excess risk in the older
subjects belonging to one of the intermediate
exposure categories, the 0.2–0.4 lT one (Table 3).
Area-specific analyses, however, did not allow to
compute valid estimates for Sicily, since only one
subject (a control) was exposed in that subgroup,
while results for the Emilia-Romagna area (with a
much higher number of exposed subjects, six cases
and 35 cases) were similar to the overall results.
Repeating the analyses restricting the database to
residentially stable subjects, who were actually
exposed to MF from power lines since 1979, did
not substantially alter the results, although for
the !0.4 lT exposure category no valid OR could
be computed (Table 4).
Discussion
In this study, we did not find evidence for an
increased risk of ALS among individuals exposed at
Aetiology of ALS associated to magnetic fields exposure 3

home to MF from high-voltage power lines, and no
dose-response relation of disease risk with exposure
intensity or length. Similar results were found in all
subgroup analyses by age, calendar period for
disease diagnosis and area of residence (i.e.
Northern and Southern Italy). Stratification for
age was of importance since the older age group is
considered to be the one less influenced by genetic
aetiology, unlike the ‘early-onset’ form of the
disease. Thus, lack of a specific association in the
older age group (which was confirmed using a
higher age cut-point – data not shown) further
strengthens the results obtained for an entire popu-
lation. Moreover, no difference in the MF-ALS
relation emerged between the two study areas,
despite their considerable differences in life-style
characteristics and environmental exposures. In
Northern Italy areas such as Emilia-Romagna are
generally characterised by more severe outdoor air
pollution induced by motorised traffic and industrial
sources and less healthy dietary habits, compared
with Southern Italy areas such as Sicily, where the
usual dietary pattern is the well-known
Mediterranean diet. However, our comparison
across different populations is weakened by the
extremely low number of exposed subjects in the
Catania province (only one control), a situation
suggesting a different power lines distribution in
Sicily compared with the Emilia-Romagna region,
probably linked to different patterns of industrial-
isation and land use. For the analysis restricted to
subjects with long residential stability, we hypoth-
esised that long-term exposure is needed for the
long induction and clinically latent periods of a
neurodegenerative disease. However, no evidence of
an association between long-term MF exposure and
enhanced disease risk emerged, and the small excess
risk identified in the subset of the study population
with exposure 0.1–0.2 lT was imprecise and accom-
panied by deficits in other categories, and no dose-
response relation emerged.
Unlike the four previous investigations carried
out in Switzerland, Brazil, Denmark and the
Netherlands (26–29), the distinctive feature of this
study was the methodology used for exposure
assessment, which was the calculation of MF
exposure based on a validated model and the
specific information on current on the power lines,
and not solely on distance to subjects’ residence.
One of these studies tried to use a similar approach
based on MF assessment, but its population did not
allow to compute valid risk estimates, since among
the 367 ALS cases only one exceeded the exposure
threshold of 0.1 lT (27). Since factors such as
current and voltage of the line have a major role in
determining the MF intensity, lack of consideration
of these variables makes any assessment of exposure
based on the simple distance to the power lines at
high risk of bias (30). For example, wideness of
corridors around power lines of the Reggio Emilia
and Modena municipalities yielding !0.1 lT may
vary from 28 m to 216 m, mainly due to differences
in load, thus showing the high potential for exposure
misclassification of an approach based on the simple
distance from power lines. However, the approach
we used, based on narrower corridors of calculated
MF exposure around the power lines compared with
previous studies based on distance to the lines, led
to the inclusion of a lower number of exposed
subjects, leading to a higher statistical imprecision of
the risk estimates as reflected by the wide confidence
intervals.
We are also aware that some factors not con-
sidered in our model may have induced some
exposure misclassification, such as the exact height
of the power lines in each point as well as the height
of the floor of the building in which the study
subjects were residing, for which we considered
average estimates. However, such factors probably
had very little effect in biasing our exposure assess-
ment. Overall, however, all these factors should have
played a limited role in inducing MF exposure
misclassification and, more importantly, such
Table 1. Distribution of cases and controls by magnetic field exposure category.
Entire study population (n¼3440)
Persons living !20 years at the same
place of residence (n¼994)
MF, lT All subjects Females Males 565 yrs !65 yrs All subjects Females Males 565 yrs !65 yrs
50.1 697/2,702 336/1,309 361/1,393 279/1,068 418/1,634 202/779 88/327 114/452 79/295 150/562
0.1 - 50.2 2/12 1/4 1/8 0/3 2/9 1/4 0/0 1/4 0/0 1/4
0.2 - 50.4 3/10 1/4 2/6 1/8 2/2 1/2 0/1 1/1 0/1 1/1
!0.4 1/13 0/7 1/6 1/9 0/4 0/5 0/2 0/3 0/4 0/1
!0.1 6/35 2/15 4/20 2/20 4/15 2/11 0/3 2/8 0/5 2/6
Table 2. Odds ratio (OR) and 95% confidence interval (CI), for
amyotrophic lateral sclerosis associated with residential magnetic
field exposure in entire study population
a
.
Entire study population (n¼3440)
MF, lT Cases/controls OR (95%CI)
50.1 697/2,702 Ref.
0.1–50.2 2/12 0.64 (0.14-2.85)
0.2–50.4 3/10 1.17 (0.32-4.26)
!0.4 1/13 0.27 (0.04-2.13)
!0.1 6/35 0.65 (0.27-1.55)
a
Using conditional logistic regression, and 50.1 lT as reference
exposure category.
4M. Vinceti et al.

possible misclassification would have likely been
non-differential, thus potentially inducing if any a
slight regression towards the null of the relative risk
estimates. In addition, collection of personal data on
the above-mentioned additional sources of MF
exposures would have been possible only using a
different study design requiring direct participation
of the study subjects, with the inherent risk of
selection bias and (differential) exposure misclassi-
fication due to refusal to participate in the study. We
also were unable to collect information about
historical residence before 1979 and therefore early
life exposure to magnetic fields from power line, a
potentially important limitation if ALS induction
and latent periods may have been much longer than
those assessed in our study.
Finally, we cannot entirely rule out the possibil-
ity of unmeasured confounding, due to the obser-
vational design of the study. However, little is known
about any life-style and environmental risk factors
for ALS (3,12,41), nor are these putative risk factors
expected a priori to be associated with residence
near high-voltage power lines and therefore to have
substantially biased our estimates. We did not
collect information about occupational history and
therefore we did not assess the potential role of
exposure to electromagnetic fields in the work
environment, for lack of available data. However, a
mailed survey with a questionnaire carried out in a
subset of 61 cases and 101 controls did not yield
evidence of a higher frequency of history of
electricity generation occupation in cases (0%)
than in controls (2%) (42).
While our results are consistent with those
carried out in the general populations assessing
MF exposure on the basis of distance from power
lines, they differ from those yielded by some
investigations carried out in occupationally-exposed
subjects (19,21,23,43). However, not all studies in
electricity workers have been consistent (22,24), and
the excess risk observed in these subjects (such as in
welders) might have been due to uncontrolled
confounding factors (44), such as electric shocks
or exposure to toxic chemicals such as heavy metals,
selenium or persistent organic pollutants
(10,12,17,25,45).
Concerning the biological plausibility of a MF-
ALS relationship, currently available evidence is
weak. Possible mechanisms include oxidative stress,
excitotoxicity mediated by glutamate, toxic effects
caused by the mutation of type 1 superoxide-
dismutase (SOD1), abnormal protein aggregation,
intermediaries filaments disorganisation, changing
the anterograde and retrograde axonal transport,
microglial activation, inflammation, and growth
factor deficiency (46,47). However, general evi-
dence linking these mechanisms to MF, particularly
for ‘low’ exposure levels to extremely low-frequency
electromagnetic fields is weak or unclear (48,49),
and results of recent specific studies on this issue
have been null (50,51), thus not providing strong
support for such an association consistent with the
null results of population-based epidemiologic
studies.
In conclusion, findings of this study, the first to
assess the relationship between amount of MF
exposure and ALS risk, do not support involvement
of the MF generated by high-voltage power lines in
disease aetiology, independently of gender, age, and
the different life-style and environmental character-
istics of the underlying areas. Although we cannot
entirely rule out that MF may be of relevance in
ALS aetiology in specific individuals, such as those
carrying genetic susceptibilities for the disease,
evidence from our study appears to confirm that
MF does not play a major role in the aetiology of this
neurodegenerative disease in the general population.
Table 3. Odds ratio (OR) and 95% confidence inter val (CI) for amyotrophic lateral sclerosis associated with residential magnetic field
exposure according to age at diagnosis, period and area of residence
a
.
Age at diagnosis Period of diagnosis Region of residence
MF, lT565 yrs !65 yrs 1998-2004 2005-2011 Emilia-Romagna Sicily
50.1 Ref. Ref. Ref. Ref. Ref. Ref.
0.1–50.2 – 0.84 (0.18-3.89) 0.67 (0.08-5.54) 0.61 (0.07-5.08) 0.64 (0.14-2.85) –
0.2–50.4 0.48 (0.06-3.86) 4.00 (0.56-28.40) 1.53 (0.30-7.91) 0.80 (0.09-6.85) 1.17 (0.32-4.26) –
!0.4 0.38 (0.05-3.11) – 0.55 (0.07-4.71) – 0.29 (0.04-2.31) –
!0.1 0.37 (0.09-1.59) 1.03 (0.34-3.11) 0.93 (0.56-1.55) 0.59 (0.26-1.35) 0.67 (0.28-1.60) –
a
Using crude conditional logistic reg ression, and 50.1 lT as reference exposure category.
Table 4. Odds ratio (OR) and 95% confidence interval (CI) for
amyotrophic lateral sclerosis associated with residential magnetic
field exposure according to residential-exposure stability
a
.
Magnetic fields
corridor (lT) Cases/controls OR (95%CI)
50.1 202/779 Ref.
0.1–50.2 1/4 0.95 (0.11-8.61)
0.2–50.4 1/2 2.02 (0.18-22.53)
!0.4 0/5 –
!0.1 versus 50.1 2/11 0.73 (0.16-3.31)
a
Using unconditional logistic regression adjusted for age and sex,
and 50.1 lT as reference exposure category.
Aetiology of ALS associated to magnetic fields exposure 5

Acknowledgements
This work was supported by AISLA (the Italian
Amyotrophic Lateral Sclerosis Association) and by
the National Health Service - Local Health Unit of
Reggio Emilia.
Declaration of interest
Dr. Kheifets received funding from EPRI (Electric
Power Research Institute) for other research activity
and not for the present study. All the remaining
authors declare no conflict of interest.
ORCID
Marco Vinceti http://orcid.org/0000-0002-0551-
2473
Tommaso Filippini http://orcid.org/0000-0003-
2100-0344
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