Exposure to environmental toxins and the risk of sporadic motor neuron disease: an expanded Australian case-control study.
ABSTRACT It remains unclear what role environmental toxins play in sporadic motor neuron disease (SMND) and its most common subtype, amyotrophic lateral sclerosis (SALS). Most previous studies of this issue have contained only small numbers of SMND cases. We sought to re-examine possible associations between toxins and SMND in a large Australian case-control study.
Questionnaire data were available from 787 patients with SMND (614 with SALS) and 778 non-related controls. Individuals were asked whether they had been exposed to metals or chemicals/solvents at work or to herbicides/pesticides. Chi-square tests with odds ratios and 95% confidence intervals were calculated for responses, and significance levels were corrected for multiple testing.
Men were more likely to acquire SALS if they worked with metals (OR = 1.95, 95% CI = 1.24-3.07) or chemicals/solvents (OR = 1.96, 95% CI = 1.46-2.61) or if they had been exposed to herbicides or pesticides (OR = 1.77, 95% CI = 1.30-2.39). Women who had worked with chemicals or solvents also appeared to be at increased risk of acquiring SALS (OR = 1.71, 95% CI = 1.22-2.40).
These results support previous reports that exposures to metals or chemicals are associated with SMND. A suggested protocol for future multinational studies of environmental toxins and SMND is presented.
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ABSTRACT: There has been a steep increase in the prevalence of dementia in recent decades, which has roughly followed an increase in pesticide use some decades earlier, a time when it is probable that current dementia patients could have been exposed to pesticides. This raises the question whether pesticides contribute to dementia pathogenesis. Indeed, many studies have found increased prevalence of cognitive, behavioral and psychomotor dysfunction in individuals chronically exposed to pesticides. Furthermore, evidence from recent studies shows a possible association between chronic pesticide exposure and an increased prevalence of dementia, including Alzheimer's disease (AD) dementia. At the cellular and molecular level, the mechanism of action of many classes of pesticides suggests that these compounds could be, at least partly, accountable for the neurodegeneration accompanying AD and other dementias. For example, organophosphates, which inhibit acetylcholinesterase as do the drugs used in treating AD symptoms, have also been shown to lead to microtubule derangements and tau hyperphosphorylation, a hallmark of AD. This emerging association is of considerable public health importance, given the increasing dementia prevalence and pesticide use. Here we review the epidemiological links between dementia and pesticide exposure and discuss the possible pathophysiological mechanisms and clinical implications of this association.Toxicology 02/2013; · 4.02 Impact Factor
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ABSTRACT: A slow but steady increase in neurodegenerative disorders has been noted in recent decades. Degenerations in the nervous system are found in Alzheimer´s disease, Parkinson´s disease and motor neuron diseases. Amyotrophic lateral sclerosis (ALS) is the most common of the motor neuron diseases. It is often considered a model disorder of neurodegeneration. Early symptoms of ALS are limb weakness or weakness in muscles of speech and swallowing. Muscle atrophy follow and a slowly progressing paralysis spreads to respiratory muscles invariably leading to death in respiratory failure. Neurophysiological investigations are necessary for proper diagnosis, and it is important to rule out treatable diagnostic alternatives such as myopathies or polyneuropathies. The cause of ALS is unknown. Prevailing theories include genetic, viral, inflammatory, oxidative or toxic mechanisms. Some indications point toward metallotoxic etiologies. Clusters of ALS have been observed in regions where geological conditions cause elevated metal concentrations in water and soil. Several studies show increased frequency of ALS in certain occupations. ALS-like conditions are found in animals, notably in horses, where metal exposure can be suspected. In addition animal metal exposure experiments show accumulations of metals in the spinal cord. The aim of this thesis project is to clarify the role of metals in ALS. The hypothesis tested is that neurotoxic metals contribute significantly to the pathogenesis of ALS. To study this we have measured concentrations of 22 metals in cerebrospinal fluid (CSF) and plasma from patients with ALS and from controls, and correlated findings to literature data to suggest a model for ALS pathogenesis. Increased concentrations were found for the metals manganese, aluminum, cadmium, cobalt, copper, zinc, lead, vanadium and uranium in CSF from patients with ALS compared to controls. Manganese showed the most prominent correlation. Simultaneous sampling from plasma did not show these elevated concentrations, indicating metal accumulations in ALS CSF. Most of the metals detected in CSF from ALS patients are neurotoxicants. Studies of mercury distribution in a monkey showed mercury accumulations in the spinal cord after respiratory exposure to mercury. Motor neurons of the spinal cord seem to be more vulnerable to metal toxicity then surrounding cells, as they lack protection from the metal-binding protein metallothionein. Patient exposure to metals, distribution by the bloodstream, penetration of protective barriers and direct toxic effects on neurons of the spinal cord is suggested to be causative in ALS. It is concluded that neurotoxic metals can reach and affect the anterior horn cells of motor neurons and thereby contribute to the pathogenesis of ALS.03/2013, Degree: MD PhD, Supervisor: Professor Monica Nordberg
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ABSTRACT: The cause of sporadic amyotrophic lateral sclerosis (SALS) remains unknown. We attempted to find out if occupational exposure to toxicants plays a part in the pathogenesis of this disease. In an Australia-wide case-control study we compared the lifetime occupations of 611 SALS and 775 control individuals. Occupations were coded using country-specific as well as international classifications. The risk of SALS for each occupation was calculated with odds ratios using logistic regression. In addition, the literature was searched for possible toxicant links between our findings and previously-reported occupational associations with SALS. Male occupations in our study that required lower skills and tasks tended to have increased risks of SALS, and conversely, those occupations that required higher skills and tasks had decreased risks of SALS. Of all the occupations, only truck drivers, where exposure to diesel exhaust is common, maintained an increased risk of SALS throughout all occupational groups. Another large case-control study has also found truck drivers to be at risk of SALS, and almost two-thirds of occupations, as well as military duties, that have previously been associated with SALS have potential exposure to diesel exhaust. In conclusion, two of the largest case-control studies of SALS have now found that truck drivers have an increased risk of SALS. Since exposure to diesel exhaust is common in truck drivers, as well as in other occupations that have been linked to SALS, exposure to this toxicant may underlie some of the occupations that are associated with SALS.PLoS ONE 01/2013; 8(11):e80993. · 3.53 Impact Factor