Risk factors for amyotrophic lateral sclerosis (ALS) such as country of residence, hard labour, intense athletic activities, heavy metal and pet exposure, skeletal trauma, surgical procedures, malignancies, and recurrent infectious disease were investigated in 77 patients and 80 controls, matching the cases for selected parameters, hard work occurred more frequently in ALS patients than in controls; hard labour, skeletal trauma and exposure to heavy metals showed a high relative risk. Some differences were detected in the clinical evolution of ALS, as defined using the Norris scale. These findings support the role of some antecedent events in causing ALS but show that they have little influence on clinical features and disease evolution.
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