MOTOR-NEURON DISEASE ON GUAM - GEOGRAPHIC AND FAMILIAL OCCURRENCE, 1956-85

We investigated the geographic and familial occurrence of motor neuron disease (MND) on Guam, and then considered etiologic hypotheses relat ed to cycad use and metal intoxication. The research was based on 303 Chamorros from Guam and 3 Chamorros from other Mariana Islands, all wi th MND onset on Guam during 1956-85. Inarajan and Umatac, two southern districts, each had, for both sexes combined, an average incidence ra te significantly higher than the corresponding overall rate for Guam. Also, for each sex, geographic patterns of incidence were significantl y related to 1) socioeconomic level (men only), 2) cycasin concentrati ons in cycad flour samples (men and women), 3) iron concentrations in water samples (men and women), 4) silicon concentrations in water samp les (men only), and 5) cobalt and nickel concentrations in soil sample s (men and women). The MND risk in susceptible sibships was about 7-28 times greater than that in the general population. The cycad hypothes is conforms somewhat better than the metal intoxication hypothesis wit h the data presented.