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Demographic trends in the Okinawa Dialysis Study (OKIDS) registry (1971-2000)
Kunitoshi Iseki1, Masahiko Tozawa, Chiho Iseki
1Dialysis Unit and Third Department of Internal Medicine, University of The Ryukyus, Okinawa, Japan. chihokun@med.u-ryukyu.ac.jp
Background:
The clinical demographics of chronic dialysis patients are changing worldwide. However, long-term data from regional dialysis registries have not yet been analyzed and reported.
Methods:
The Okinawa Dialysis Study (OKIDS) registry included all chronic dialysis patients treated in Okinawa, Japan, since 1971. Data for the years 1971 to 1990 were analyzed to predict trends for 1991 to 2000. The predicted values were then compared to the actual values and analyzed statistically, with particular attention being paid to relative risk of death. Multivariate Cox proportional hazards analysis was done to analyze the time factors of relative risk of death.
Results:
A total of 5246 patients (2981 men and 2265 women) were registered and the total duration of observation was 28,431 patient-years. The prevalence and incidence of dialysis patients expressed per million population were 2320 and 297, respectively, in 2000, values that were significantly higher (P < 0.02 for both) than the predicted values. The gross mortality rate per 1000 patient-years was 118.4 for 1971 to 1980, 63.3 for 1981 to 1990, and 77.7 for 1991 to 2000. The adjusted hazards ratio (95% confidence interval) for mortality was 0.743 (0.650 to 0.862) for 1981-1990 and 0.721 (0.659 to 0.790) for 1991 to 2000 in comparison to the risk of mortality in 1971 to 1980. The decrease in mortality rate was largely due to the drop in cardiac deaths from 71.0 for 1971 to 1980 to 17.2 for 1991 to 2000.
Conclusions:
The incidence and prevalence of chronic dialysis patients increased more than expected over the past decade in Okinawa, Japan. Despite the rapid change in patient demographics, the survival rate did not decrease significantly.