Why has the gross mortality of dialysis patients increased in Japan?

Background. The gross mortality of Japanese chronic dialysis patients gradually increased from 8.1% in 1983 to 9.4% in 1997. We describe the demographic changes in dialysis patients and clarify why the gross mortality has increased. Methods. Data used in our analysis were taken from annual reports by the Patient Registration Committee of the Japanese Society for Dialysis Therapy. The relative risk of death was calculated by a logistic regression procedure and Cox proportional hazard model. Results. The first-year survival starting from the initiation of dialysis therapy slowly improved from 0.836 in 1983 to 0.857 in 1996, but 5-year and 10-year survival consistently decreased in the same patient groups. The patients' mean age of beginning dialysis steadily increased from 51.9 in 1983 to 62.2 in 1997. The incidence of patients with diabetes as the original disease showed a tremendous increase from 15.6% in 1983 to 33.9% in 1997, and patients with nephrosclerosis also showed a twofold increase in our population. Heart failure accounted for 30-35% of mortality until 1991, but this started to decrease after 1992, when recombinant human erythropoietin became clinically available, and the level fell to 23.9% by 1997. The relative risk of death in the first year of initiating dialysis therapy decreased to almost half of the reference year 1983 (P < 0.0001). Conclusion. The increase in the gross mortality of Japanese dialysis patients might not be due to a deteriorating quality of dialysis therapy, but rather is a reflection of accepting patients with older age and comorbid factors contributing to higher risks of mortality with dialysis therapy.