After five years, hemodialysis was associated with lower mortality risk than peritoneal dialysis.

LONDON, Ont.—Patients on peritoneal dialysis (PD) live longer than those on hemodialysis (HD), at least during the first years after dialysis starts, a new study suggests. A question remains, however, whether it is the type of dialysis that makes the difference in survival.

The study of patients in the Canadian Organ Replacement Register showed that PD patients were significantly more likely to be alive up to five years after their dialysis began than were HD patients. After five years, the scales tipped in favor of HD, the investigators reported.

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Karen Yeates, MD, MPH, of Queen’s University in Kingston, Ont., and four co-investigators identified all patients who started renal replacement therapy between January 1, 1991, and December 31, 2000, and followed them in the register until the end of 2005. During that period, 8,946 patients were on PD and 23,434 were on HD. The mean ages of the PD and HD patients were 58.8 and 61.4 years, respectively. Males outnumbered females by a ratio of 3:2.

HD patients were 39%-48% more likely than PD patients to die within the first six months of starting dialysis. This tapered off as time went by, falling to a 2%-20% reduced risk of death with PD at 54-60 months. Then, after 60 months, HD was associated with a 4%-20% lower risk of death.

Dr. Yeates noted that study results may have been affected by confounding factors. “There are always risks and inherent weaknesses in interpreting observational data, despite the fact that we adjusted well and did a very robust analysis using the time-dependent intention-to-treat and as-treated models,” said Dr. Yeates, who presented her group’s findings at the Canadian Society of Nephrology annual meeting.

Kerri Cavanaugh, MD, MHS, assistant professor in the nephrology division at Vanderbilt University Medical Center in Nashville, agreed that various factors could have influenced the mortality differences.

“The confounding factors are very difficult to capture, despite adjustment in the statistical models, and may include complexity of comorbid illness, physical function, cognitive skills, or even such things as social support or socioeconomic status,” Dr. Cavanaugh said.