Epidemio-environmental studies on amyotrophic lateral sclerosis in the Kii Peninsula of Japan : Active or disappearing focus?

近三十年来，日本纪井半岛和关岛的肌萎缩性侧索硬化症（ALS）发病率稳步下降。与关岛不同的是，Kii半岛中心之一的Kozagawa的人口从1955年到1990年大幅减少了约50%。这引发了一个问题，即易患ALS的小川人是否已经从这个高风险地区移民出去，导致了“焦点灭绝”。1959-1971年的流行病学环境研究表明，Kii半岛向南方向，随着地区河流钙、镁含量的降低，年平均死亡率呈上升趋势。然而，在1985-1994年期间，这种负相关性消失了，对应于Muro区（Kii最南端）ALS疫源地的消失。因此，在1989-1993年期间，我们调查了和歌山县ALS患者的发病率和迁移模式，包括一个高发病率的Kii半岛疫源地（“Kozagawa疫源地”），以检验疫源地是否真正消失。5年间共观察到77例ALS患者，平均发病年龄为61.8岁。总体而言，年平均发病率为每10万人1.43例（男性2.23例，女性0.71例）；对日本1990年人口进行年龄调整后，该比率为1.25（按性别分别为1.85和0.61）。按年龄和性别划分的年平均发病率在60 - 69岁年龄段最高，男性和女性合计最高5.31；男性8.88分，女性2.36分。和歌山县五个地区的比率从0.38到2.48不等。从地理上看，高发区主要分布在中南部地区；小川地区发病率最高，为9.54例（5年2例；1990年基础人口4193例）。在研究期间，四名来自小川的移民在离开焦点十到四十年后患上了渐冻症。尽管人们认为ALS的显著聚集性已经消失，但Kii半岛南部仍然是ALS的高风险地区，特别是如果将数据解释为包括移民的话。总体而言，在过去20年中，发病年龄从56.5岁增加到61.7岁；男性的优势是显而易见的。少

The past thirty years, the frequency of amyotrophic lateral sclerosis (ALS) has steadily declined in the Kii Peninsula of Japan as well as Guam. Unlike Guam, the population of Kozagawa, one of the Kii Peninsula foci, has greatly decreased, by about 50%, from 1955 to 1990. It raises a question whether Kozagawa people predisposed to ALS have emigrated from this highrisk area, resulting in "focus extinction".Previous epidemio-environmental studies (1959-1971) showed that toward the south in the Kii Peninsula, average annual mortality rates increased along with a decrease of Ca and Mg contents in area rivers. However, during the period from 1985-1994, this negative correlation disappeared, corresponding to the disappearance of ALS foci in the Muro district (southernmost Kii).During the period of 1989-1993, therefore, the incidence rates and migration patterns of patients with ALS in Wakayama Prefecture, including one of the high-incidence Kii Peninsula foci ("Kozagawa focus"), were surveye … More d to examine whether the focus truly disappeared or not. During the 5 years, 77 ALS patients were observed with an average age at onset of 61.8 years. Overall, the average annual incidence rate was 1.43 per 100,000 population (2.23 for males and 0.71 for females) ; when age-adjusted to the Japanese 1990 population, it was 1.25 (1.85 and 0.61 respectively by gender). Average annual age- and sex-specific incidence rate was the highest in the 60 to 69-year range, with a peak of 5.31 for both males and females combined ; 8.88 for men and 2.36 for women. The rates varied in the five regions of Wakayama Prefecture from 0.38 to 2.48. Geographically, the areas with high incidence were distributed in the central and southernmost regions ; the highest being in the Kozagawa focus with 9.54 (two ALS cases for the five years ; 4,193 base population, 1990). During the study period, four emigrants from Kozagawa had developed ALS one to four decades after leaving the focus.Although the remarkable clustering of ALS had been thought to have disappeared, the southern Kii Peninsula remains a high-risk area for ALS,especially if one interprets the data so as to include the emigrants. In general, the age at onset has increased on the past 20 years from 56.5 to 61.7 ; and male predominance is noted. Less