Abstract
An interim report of a case-control study was conducted to explore the role of environmental factors in the development of amyotrophic lateral sclerosis (ALS). Sixty-six cases and 66 age- and gender-matched controls were recruited. Detailed information regarding residence history, occupational history, smoking, physical activity, and other factors was obtained using questionnaires. The association of ALS with potential risk factors, including smoking, physical activity and chemical exposure, was investigated using conditional logistic regression models. As compared to controls, a greater number of our randomly selected ALS patients reported exposure to fertilizers to treat private yards and gardens and occupational exposure to pesticides in the last 30 years than our randomly selected control cases. Smoking, occupational exposures to metals, dust/fibers/fumes/gas and radiation, and physical activity were not associated with ALS when comparing the randomly selected ALS patients to the control subjects. To further explore and confirm results, exposures over several time frames, including 0–10 and 10–30 years earlier, were considered, and analyses were stratified by age and gender. Pesticide and fertilizer exposure were both significantly associated with ALS in the randomly selected ALS patients. While study results need to be interpreted cautiously given the small sample size and the lack of direct exposure measures, these results suggest that environmental and particularly residential exposure factors warrant close attention in studies examining risk factors of ALS.
Highlights
Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder involving primarily upper and lower motor neurons in the cerebral cortex, brainstem, and spinal cord [1]
The objective of this paper is to evaluate potential environmental risk factors for ALS using a case-control study conducted in the State of Michigan
Differences in education were maintained for both males and females, but differences in marital status were found only among males (Table S1)
Summary
Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder involving primarily upper and lower motor neurons in the cerebral cortex, brainstem, and spinal cord [1]. ALS patients often experience difficulty talking, swallowing, breathing and walking, and often develop respiratory insufficiency which is the main cause of death. Approximately 5–10% of ALS cases can be attributed to genetic factors, the underlying cause of ALS remains largely unknown [8]. A number of epidemiologic studies have suggested that ALS patients have been exposed to environmental toxins [9,10,11,12,13]. Environmental risk factors investigated have included, among others, exposures to agriculture chemicals, heavy metals, solvents, electrical magnetic fields (EMF), and exercise [9,12,14,15,16]. Results have varied widely in the 40+ epidemiologic studies that have investigated such factors, and an understanding of causal links to environmental agents remains elusive
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