[Mutual relationship between prevalence statistics and mortality statistics in Parkinson's disease]

The purpose of this study is to determine whether the statistics from three published reports on Parkinson's disease (PD) are mutually interrelated and to clarify the relationship between the prevalence statistics and mortality statistics of PD. These statistics included data on "number of patients with PD (PD Patients)", "number of patients with PD receiving financial aid for treatment (PD Recipients)" as an indicator showing the prevalence of PD, and "number of deaths from PD (PD Deaths, i.e., mortality)".

The data on PD Patients, PD Recipients and PD Deaths were cited from "Patient Survey" by Ministry of Health, Labour and Welfare, a report by the Research Committee on Epidemiology of Intractable Diseases and "Vital Statistics of Japan" by Ministry of Health, Labour and Welfare, respectively. The expected PD Patients, PD Recipients and PD Deaths were calculated as products of their respective rates for the entire country and prefecture population, adjusting for a difference in population composition. Observed/expected number ratios (O/E ratio) of PD Patients, PD Recipients and PD Patients were calculated by prefecture. The correlation between the O/E ratios was examined. In addition, the relationships of the O/E ratios with the number of hospitals or physicians per person were examined.

There were no significant correlations between the O/E ratios of PD Patients, PD Recipients or PD Deaths. The O/E ratio of PD Recipients significantly correlated with the numbers of hospitals and physicians per person.

PD Patients and PD Recipients were included in number of people with PD and PD Deaths was derived from people with PD. However, these statistics do not necessarily reflect the prevalence of PD in each prefecture. When using these published statistics as an indicator of the prevalence of PD, it is necessary to clarify the purpose of their use and to comprehend their characteristics.