Are the endemic motor neuron diseases of Guam really disappearing?

Death certificates were reviewed to observe trends in the number of persons on Guam reported to have chronic degenerative motor neuron diseases (amyotrophic lateral sclerosis, parkinsonism-dementia or Parkinson's disease) at the time of death. Additional data, including age and race of the deceased and the name of the certifying physician were also collected. The number of persons having been diagnosed with amyotrophic lateral sclerosis is apparently decreasing while their mean age is increasing suggesting that the etiologic agents or factors causing this disease are less prevalent on Guam today than they have been in the past. Trends with regard to parkinsonism-dementia and Parkinson's disease are less clear.