Risk factors in the early diagnosis of ALS: North American epidemiological studies

Patient-specific (endogenous) and population-specific (exogenous) risk factor analysis is identifying novel physical and chemical exposures which might be time-linked to the development of amyotrophic lateral sclerosis (ALS) and other motor neuron diseases. Electric injury in a number of case-control studies as well as prolonged exposure at work and home to agricultural chemicals in pesticides and herbicides have been identified as significant risk factors. Heavy exercise, trauma with or without bone fractures and heavy metal exposure at work have not been confirmed as risk factors. Surprisingly, occupation as a pilot or navigator has recently been identified as a potential risk factor, which will need to be confirmed. The introduction of international patient registries in North America (ALS CARE) and in Europe (ALS HPS) will facilitate future studies on the prognosis of ALS, adherence to standards of practice, quality of life and patient outcome studies. An initial survey of the ALS Patient Care Database in January 1999, when nearly 1800 patients had been entered across North America, indicated the median time from ALS onset to diagnosis is 14 months when no second opinion is requested, 12 months if the patient requests a second opinion and 10 months when the neurologist requests an additional opinion. No significant difference was found in the median time to diagnose sporadic ALS patients compared with familial ALS patients.