Incidence of Parkinson disease in Wakayama, Japan.

To estimate an accurate annual incidence of Parkinson disease in Wakayama, a mail survey was conducted in 1998. A questionnaire was delivered to each clinic where Parkinson disease would be potentially diagnosed. The survey was conducted in February 1998 by the Research Committee on Parkinson disease of Wakayama. A total of 792 clinics and 87 hospitals were listed as candidates. Physicians in these 879 medical facilities were asked and instructed to register all newly diagnosed patients with Parkinson disease in 1997 according to the diagnostic criteria proposed by the Japanese Research Committee on Neuro-degenerative Diseases. Of 879 facilities, 873 ones including 81 hospitals replied (response rate: 99%). A total of 229 patients were reported as newly diagnosed cases in 1997. Of these cases, 183 cases were classified as Yahr I to III. The annual incidence rate was 16.9 per 100,000 population (95% confidence interval: 14.5-19.3). Male-to-female ratio was 1:1.4 as a whole, and the dominant age stratum was 70 to 79 years old. When Parkinson disease incidence was observed from northern part of Wakayama to south by district, crude rates (95% CIs) were 15.9(12.9-18.9), 18.1(12.0-24.2), and 19.3(13.4-25.2). After age-adjustment using the Japanese Model Population in 1985, differences of Parkinson disease incidence became attenuated and adjusted rates (95% CIs) turned to 10.8(9.1-12.7), 10.4(8.6-12.2), and 9.9(6.9-12.9), respectively.