KOHMOTO Junko Assistant Lecturer, Department of Neurology, Wakayama Medical College, 医学部, 助手 (90254557)
KIHARA Tameko Assistant Professor, Department of Neurology, Wakayama Medical College, 医学部, 講師 (30225015)
|Budget Amount *help
¥1,000,000 (Direct Cost : ¥1,000,000)
Fiscal Year 1999 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 1998 : ¥400,000 (Direct Cost : ¥400,000)
Although the remarkable clustering of ALS had been thought to have disappeared, the southern Kii Peninsula remains a high-risk area for ALS/PDC. A review of death certificates of patients with ALS was conducted in the Mie, Nara and Wakayama prefectures in the Kii Peninsula of Japan, from 1962 to 1994. For these 22 years, 799 ALS cases were found ; 472 male and 372 female cases (male to female ratio : 1.44 to 1).
Age-adjusted annual mortality rates of the three prefectures were gradually averaging to 0.9 per 100,000 population at the end of the period. In this period, the average age at death increased from 58.4 to 64.5 years old. In Mie prefecture, the mortality rates slightly increased from 0.79 to 0.9 ; the mortality rate in Mie prefecture from 0.5 to 0.89. On the contrary, the mortality rates in Wakayama prefecture decreased from 1.24 to 0.93. However, the mortality rates in the southern part of the Kii Peninsula still maintained higher rates.
Based on the above mortality studies, it
revealed that toward the south in Wakayama and Mie prefectures, the standardized mortality rates (SMR) were increasing with a decrease of Ca and Mg contents in area's rivers : the highest mortality rates and lowest Ca and Mg contents in the southern part of the Kii Peninsula. Thus, the mortality rates strongly and negatively correlated with the Ca and Mg contents in the rivers. After 1980, this tendency, however, disappeared. In Oshima Island at the bottom of the Kii Peninsula, the drinking water from wells and streams showed exceptionally high contents of Ca and Mg in the southern Muro district. We have observed no ALS patients in this island over forty years.
In the latest prevalence survey on January 1, 2000, a crude prevalence was 71.5 in Kozagawa, including one ALS and two PDC-ALS cases, showing dementia, parkinsonism and amyotrophy with pathological and pyramidal signs. The two PDC-ALS cases were each found in an ALS family in Kozagawa area. In the previous surveys, we had not found any PDC-ALS case in this area. In Oshima Island, there have been no PDC/ALS cases.
Just as in the southern village of Guam (Lavine et al., 1991), the determination of continuation of the disease in the Kozagawa focus of the Kii peninsula is really dependent on the intensity of follow-up studies, and particularly the need for house -to-house surveys. Less