Researchers have provided more evidence that exposure to toxic
environmental pollutants raises the risk for amyotrophic lateral
sclerosis (ALS).
Unlike previous research, the new study used both surveys and measurement of toxic chemicals in blood.
"This
is not going to alter treatment at this point, but it really helps us
think about the types of things we can do to prevent ongoing leakage of
chemicals, and limit the pollution that we put into the environment,
because it does have an impact, we believe, on disease," study author
Stephen A. Goutman, MD, assistant professor and director, ALS Clinic,
University of Michigan, Ann Arbor, told Medscape Medical News.
The study was published online May 6 in JAMA Neurology.
From
a tertiary center in Michigan, researchers identified 156 patients with
ALS and recruited 128 controls with no ALS or family history of any
neurodegenerative disorder.
They determined likely exposures
through self-administered questionnaires on occupational and residential
history, and military service, and collected other information on
smoking history and demographic characteristics.
From
blood samples, they examined concentrations of 122 environmental
organic pollutants, including organochlorine pesticides (OCPs),
polychlorinated biphenyls (PCBs), which were chemicals used as coolants
or lubricants in electrical equipment, and brominated flame retardants
(BFRs).
Investigators accounted for confounding variables,
including tobacco use, age, sex, education level, marital status,
ethnicity, and military service.
The analyses showed a consistent association between occupational
pesticide exposure and ALS. For any past exposure, the odds ratio (OR)
was 5.09 (95% confidence interval [CI], 1.85 - 13.99; P < .01).
Ever having worked for the US Armed Forces was also associated with increased ALS risk (OR, 2.31; 95% CI, 1.02 - 5.25; P < .05).
Military Link
The
link between being in the armed forces and ALS isn't new, said Dr
Goutman. Theories possibly explaining the association include increased
exposure to chemicals used during conflicts (especially during the first
Gulf war), increased physical activity, multiple vaccinations, and
traumatic injury.
Unexpectedly,
occupational exposure to lead showed a statistically significant
protective effect for ALS (OR, 0.32; 95% CI, 0.13 - 0.81; P < .05).
Dr
Goutman said this requires additional follow-up but pointed out that
lead was not measured in blood and that the protective effect was seen
only when the authors looked at occupational exposure recalled over a
lifetime, not at individual exposure time windows of susceptibility.
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