Factors Associated with Mortality in Patients with End-Stage Renal Disease During the First and Second Years After a Dialysis Initiation
Mortality is high among incident hemodialysis patients especially during the first several months after initiation of dialysis and can be influenced by many factors. Age, vascular access, co-morbid conditions, serum levels of albumin, and dialysis modality may affect survival. We attempted to identify factors that influence survival of incident hemodialysis patients and to determine if changes in clinical practices could improve survival. We hypothesized that patients surviving at least 24 months differ in their characteristics from those who died and so indentifying those differences and making changes may improve survival in all hemodilaysis patients.
Standardized mortality ratios (SMR) were calculated for each of the first 24 months on dialysis to determine the temporal pattern of mortality. Cox proportional hazard models were fitted to examine mortality at several a priory determined time periods for each predictor using case-mix adjustments. The associations between all-cause mortality and combined serum levels of albumin and nPCR were studied for each of first 8 quarters on dialysis. Changes in serum albumin and nPCR levels from the prior quarter were examined separately. Finally, marginal structural models (MSM) were fitted to analyze the association between mortality and dialysis modality during 24 months of treatment. Inverse probability weights were created to account for time varying confounding of quarterly measured laboratory values and changes in dialysis modality over the first 8 quarters.
SMRs were the highest during the 3-6 months after starting dialysis. Use of central venous catheters and low levels of serum albumin at the time of dialysis initiation were associated with all-cause and infection-related mortality during the first 24 months of treatment. Volume overload was associated with cardio-vascular mortality especially in non-hypoalbuminemic patients. Decrease in albumin and nPCR was associated with mortality during 24 months on dialysis. Patients on peritoneal dialysis showed better survival compared to hemodialysis patients after adjusting for modality changes by using MSMs. Patients who changed modalities at least once showed a survival advantage over those who remained on initial modality during 24 months of dialysis treatment.