title: The higher risk of death on peritoneal dialysis in the United States is not explained by background general population mortality: the CANUSA study revisited.
abstract: The CANUSA investigators reported a near doubling of the risk of death in peritoneal dialysis patients treated at U.S. sites compared to Canadian centers. Recently, evidence has suggested that background mortality rates in the general population might be responsible for differences in death rates on dialysis. The objective of this study was to determine if differences in background mortality in the general population were responsible for the increased risk of death observed in American patients in the CANUSA study. The CANUSA study was a prospective cohort study of 680 consecutive peritoneal dialysis patients at 14 centers in the U.S. and Canada. Extensive baseline data were available for all patients. The expected mortality rate of an individual of the same age, sex, and country of residence was determined at the time of enrollment in the CANUSA study. Cox proportional hazards models were used to determine if background mortality rates were responsible for the observed differences in survival between the two countries. Background mortality rate in the general population was associated with an increased risk of death on peritoneal dialysis, but after adjustment for other baseline factors, it was no longer significant. The adjusted, relative hazard of dying in the U.S. compared to Canada was unchanged after further adjusting for background mortality rate in statistical models (HR = 1.93; 95% confidence interval: 1.13 - 3.28). In conclusion, the increased risk of mortality in U.S. patients enrolled in the CANUSA study was not explained by differences in the background mortality rate in the general population.
authors.affiliation: Sunnybrook Health Sciences Center, Foothills Medical Centre, Calgary, Alberta, Canada. robert.quinn@sunnybrook.ca
authors.forename: R R
authors.initials: RR
authors.lastname: Quinn
authors.forename: K E
authors.initials: KE
authors.lastname: Thorpe
authors.forename: J M
authors.initials: JM
authors.lastname: Bargman
mesh_terms: D000367:Age Factors; D002170:Canada / Q000453:epidemiology; D006801:Humans; D018579:Patient Selection; D010530:Peritoneal Dialysis / Q000401:mortality*; D016016:Proportional Hazards Models; D012042:Registries; D012306:Risk; D012307:Risk Factors; D012720:Severity of Illness Index; D014481:United States / Q000453:epidemiology; D014850:Waiting Lists