# Estimating Short-Term and Long-Term Survival for Patients With Kidney Failure Using a Mixture Survival Model

## TL;DR

A new survival model reveals racial disparities in long-term outcomes for kidney failure patients, showing that Black and American Indian patients have better short-term but worse long-term survival compared to White patients.

## Contribution

The study introduces a mixture survival model to distinguish short-term and long-term survival in kidney failure patients, uncovering hidden disparities not captured by traditional models.

## Key findings

- Black and American Indian patients had better short-term survival but worse long-term survival odds compared to White patients.
- The mixture model revealed that American Indian patients were 1.59 times more likely to not have long-term survival than White patients.
- Socioeconomic and geographic factors were linked to survival disparities in kidney failure patients.

## Abstract

Traditional survival models assume all patients receiving kidney replacement therapy (KRT) may be grouped into one population, overlooking long-term survivors, particularly successful transplant recipients, and may fail to appreciate the disparities in minority populations. On the other hand, a mixture survival model allows for the estimation of hazard and odds ratios of all-cause mortality in patients with kidney failure undergoing either dialysis or transplantation.

This retrospective cohort study analyzed survival outcomes using a proportional hazards mixture survival model, comparing results to a traditional Cox proportional hazards model with time-varying modality of treatment.

Data from the United States Renal Data System included 2,228,693 patients initiating KRT between 2000 and 2020.

Key predictors included demographics, comorbid conditions, socioeconomic status, geographic location, and rurality.

The primary outcome was all-cause mortality. The mixture survival model distinguishes between patients’ characteristics associated with long-term survival (ie, primarily those with successful transplants) and short-term survival (ie, those at a greater risk of mortality over time, such as patients treated with dialysis).

Both a Cox proportional hazards model and a proportional hazards mixture survival model were applied to all patients.

Findings from both models were largely consistent, but the mixture survival model revealed new insights into racial disparities. In the Cox model, American Indian individuals had an adjusted hazard ratio of 0.63 compared with White individuals (95% CI. 0.62-0.63) and 0.74 for Black individuals compared with White (95% CI, 0.74-0.74). The mixture model confirmed these trends but also showed that American Indian individuals were 1.59 times more likely to not have a long-term survival than White individuals (95% CI, 1.415-1.797) and Black individuals were 1.35 times more likely to not be in the long-term surviving group than White individuals (95% CI, 1.310-1.397). Additional disparities were observed by socioeconomic and geographic factors.

Data collected at the beginning of dialysis may not fully capture patients’ health trajectories.

The mixture survival model provides a more comprehensive understanding of mortality disparities for patients with kidney failure receiving KRT by distinguishing between short-term and long-term survivability. The findings highlight the need for targeted interventions to improve long-term outcomes for minority patients.

Kidney failure affects minority groups at a high rate, but much of the current research explores a few of these groups versus a more inclusive approach. Therefore, we examined survival outcomes in over 2 million US patients with kidney failure who received dialysis or a kidney transplant. The results showed that Black and American Indian patients with kidney failure had better short-term survival but worse long-term survival odds as compared with White patients, and disparities were linked to age at first dialysis, socioeconomic and geographic factors. By using the mixture survival model, the study provided new insights into who is more likely to live longer after starting dialysis or receiving a transplant. This provides a base of evidence to develop interventions targeted at improving long-term survival and health outcomes for underserved and isolated patient populations with kidney failure.