Parkinsonism Before and Since the Epidemic of Encephalitis Lethargica

Abstract

Several observers have noted that the population of patients afflicted with parkinsonism seems to have increased in age over the past two or three decades.^1-3 Recently, Poskanzer and Schwab reported that the age of onset in cases observed at the Massachusetts General Hospital has gradually increased from a mean of 32.4 in the period 1920-1924 to a mean of 59.4 in the years 1955-1959.⁴ They have presented these data as evidence that all—or nearly all—cases of parkinsonism prevalent today represent a cohort of survivors of the epidemic of encephalitis lethargica of 1917-1926 and have gone on to predict that parkinsonism will consequently largely disappear by 1980. It will persist thereafter, according to these authors, only in the form described by James Parkinson which will constitute a numerically insignificant disease entity. To those charged with the care of the Parkinson patient, or engaged in research in parkinsonism and related