Geographic patterns of parkinsonism-dementia complex on Guam. 1956 through 1985
Z. X. Zhang, D. W. Anderson and N. Mantel
Neuroepidemiology Branch, National Institute of Neurological Disorders and Stroke, Bethesda, Md 20892.
Average annual age-adjusted incidence rates of parkinsonism-dementia
complex were obtained for the 19 election districts of Guam from 1956
through 1985. The highest rates were found in the southern and central
districts, and the lowest rates were found in the northern and western
districts. Geographic and temporal patterns of incidence were associated
with socioeconomic status but not with geochemical factors. The risk of
parkinsonism-dementia complex in susceptible sibships was much higher than
that in the general population--even in districts with the highest
incidence rates, but especially in districts with the lowest incidence
rates. Our evidence tends to support the hypothesis that multiple factors
linked to cycad use play an important role in the cause of PDC. Hypotheses
related to metal exposure and simple genetic factors were unsatisfactory
explanations for the epidemiologic patterns observed.
