Epidemiology of Parkinson's disease in Yonago City, Japan: comparison with a study carried out 12 years ago.

A study of the prevalence of Parkinson's disease (PD) was conducted in a Japanese city in 1992, and the data compared with those of a similar study performed in 1980. On the prevalence day, April 1, 1992, a total of 156 patients (46 males and 110 females) were found to be living in the investigated area, which had a population of 132,315. The prevalence per 100,000 population was 117.9 (72.8 in males and 159.1 in females), and the incidence during the period 1989 through 1992 was 15.0 per 100,000 population per year. The age- and sex-adjusted prevalence per 100,000 population was 99.5 in 1992 and 103.9 in 1980, as calculated using the 1990 Japanese population as the standard. The age-adjusted prevalence in the population under 60 years of age and the incidence in those under 55 years of age in 1992 were lower than in those under 55 in 1980. These results revealed that changes in the age structure of the population were the main contributors to the increased incidence of PD.