RELATIONSHIP OF DOSE OF HEMODIALYSIS AND CAUSE-SPECIFIC MORTALITY

A number of studies have found a relationship of lower all-cause morta lity risk for ESRD patients treated with increasing dose of dialysis. The objective of this study was to determine the relationship of deliv ered dose of dialysis with cause-specific mortality. Data from the USR DS Case Mix Adequacy Study, which includes a national random sample of hemodialysis patients, were utilized. To minimize the contribution of unmeasured residual renal function, the sample used in this analysis (N = 2479) included only patients on dialysis for one year or more. Co x proportional hazards models, stratified for diabetes, were used to a nalyze the effect of delivered dose of dialysis (measured and reported by both Kt/V and URR) on major causes of death and withdrawal from di alysis, adjusting for other covariates including demographics, comorbi d diseases present at start of study, functional status, laboratory va lues and other dialysis parameters. Patient follow-up for mortality wa s censored at the earliest of time of transplantation, 60 days after a switch to peritoneal dialysis or at the time of data abstraction. For each 0.1 higher Kt/V, the adjusted relative risk of death due to coro nary artery disease was 9% lower (RR = 0.91, P < 0.05), due to other c ardiac causes was 12% lower (RR = 0.88, P < 0.01), due to cerebrovascu lar disease (CVD) was 14% lower (RR = 0.86, P < 0.05), due to infectio n was 9% lower (RR = 0.91, P = 0.05), and due to other known causes wa s 6% lower (RR = 0.94, P < 0.05). There was no statistically significa nt relationship of Kt/V and risk of death among patients who died of m alignancy (RR = 0.84, P = 0.10) or among patients whose death cause wa s missing (RR = 0.95, P = 0.41). The risk of withdrawal from dialysis prior to death due to any cause was 9% lower (RR = 0.91, P < 0.05) for each 0.1 higher Kt/V. The relationships of delivered dose of dialysis , as measured by URR, and cause specific mortality were essentially si milar in relative magnitude and statistical significance as the relati onships observed using Kt/V as the measurement of dialysis dose, with the exception that the relationship was less significant for cerebrova scular disease and withdrawal from dialysis. The relationship of dialy sis dose with risk of death due to each cause of death category except other cardiac causes and ''other'' causes appeared to be of greater m agnitude and of greater statistical significance among diabetics than non-diabetics. These results indicate that low dose of dialysis is not associated with mortality due to just one isolated cause of death, bu t rather is due to a number of the major causes of death in this popul ation. This study is consistent with hypotheses that low doses of dial ysis may promote atherogenesis, infection, malnutrition and failure to thrive through a variety of pathophysiologic mechanisms. Further stud y is necessary to confirm these results and to test hypotheses that ar e developed.