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Amyotrophic Lateral Sclerosis (ALS) and Parkinsonism Dementia (PD) are two important neurodegenerative disorders that exhibited extremely high incidence rates within 3 foci of the Western Pacific: the Kii Peninsula of Japan, the Auyu and Jakai speaking people of Western New Guinea, and the Chamorros of Guam in the Mariana Islands. ALS is caused by a degradation of the motor neurons in the brain and spinal cord leading to a progressive weakness and atrophy of skeletal muscles. Patients with PD exhibit slowness of motor activity, disturbances in gait and a loss of cognitive function. From the latter half of the 20th century, reported incidence rates of ALS and PD in these foci were hundreds and even a thousand times greater than the incidence rates in the United States and elsewhere globally. Our epidemiological analysis demonstrates that the high incidence of ALS and PD in these foci has dramatically declined and was accompanied by an older patient age of onset alongside a change in the male to female sex ratio from more than 2:1 to near unity today. Having occurred within families of first degree relatives, the declination was thought to have been due to unknown genetic factors. However, increasing modernization and shifts in lifestyle and cultural practices suggest the causal factors are likely environmental. This study will detail our epidemiological findings, and summarize the ecological and experimental data in support of two long- standing environmental hypotheses involving candidate neurotoxins as a cause of ALS and PD in these foci.



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Disappearance of High Incidence Amyotrophic Lateral Sclerosis and Parkinsonism Dementia in the Western Pacific: Clues to their Etiology