Trends in mortality on peritoneal dialysis: Canada, 1981-1997

Several technical and nontechnical improvements in peritoneal dialysis (PD) have occurred during recent years. Since few previous studies have examined trends in PD mortality over time, and to determine whether enhancements in PD have translated into improved patient outcomes, mortality rates among the 17,900 patients receiving PD in Canada during the period 1981-1997 were analyzed. Mortality rate ratios (RR) were estimated using Poisson regression, adjusting for age, race, gender, primary renal diagnosis, follow-up time, and type of PD (continuous ambulatory/cyclic versus intermittent). Adjusted mortality rates decreased significantly by calendar period, the reduction being monotonic: RR = 0.81, 95% confidence interval [CI], 0.75 to 0.87 for 1986-1989; RR = 0.73, 95% CI, 0.67 to 0.78 for 1990-1993; RR = 0.63, 95% CI, 0.58 to 0.67 for 1994-1997, with 1981-1985 serving as the reference period (RR = 1, fixed). The improvement in mortality was fairly consistent across patient subpopulations. When analyzed separately by follow-up time window, the mortality decrease was strongest in the first 12 mo after renal replacement therapy initiation. Supplementary analysis revealed that the trend in mortality rates was not attributable to corresponding trends in transplantation or technique failure rates, or modality switching patterns. Results were quite similar whether based on an "as-treated" or "intent-to-treat" analysis. More extensive data on practice patterns would empower future studies to elucidate the cause/effect relationship between PD practice patterns and patient survival.