Risk Factors for Mortality in COVID-19 Patients on Long-Term Dialysis

Risks for adverse outcomes associated with COVID-19 are increased in patients with pre-existing conditions, including obesity, diabetes, or chronic cardiovascular, lung, liver, and kidney diseases. There is also evidence of disparities based on sex, race, and region in the United States.

Patients with end-stage kidney disease (ESKD), particularly those with additional comorbidities, are at higher risk of worsened prognoses with COVID-19. Patients with ESKD undergoing in-center maintenance hemodialysis are extremely susceptible to SARS-CoV-2 infection. Previous studies have examined the impact of COVID-19 on dialysis patients in specific regions or within specific dialysis organizations.

However, according to Stephen Salerno, MS, and colleagues, there are few data available on outcomes in COVID-19 in a national population of patients receiving long-term dialysis. The researchers conducted a retrospective, claims-based cohort study to identify risk factors associated with COVID-19 and mortality in Medicare patients undergoing long-term maintenance dialysis. Results of the study were reported in JAMA Network Open [doi:10.1001/jamanetworkopen.2021.35379].

The study compared mortality trends of patients receiving long-term dialysis in 2020 with those of previous years (2013-2019) and fit Cox regression models to identify risk factors for contracting COVID-19 and postdiagnosis mortality. The primary outcomes of interest were COVID-19 and all-cause mortality. Associations of claims-based risk factors with COVID-19 and mortality were examined pre- and postdiagnosis.

Among the cohort of 498,169 Medicare patients undergoing dialysis, median age was 66 years, and 43.1% (n=215,935) were women and 56.9% (n=283,227) were men. Most (94%) lived in an urban area. Of the total cohort, 12.1% (n=60,090) received a diagnosis of COVID-19 during the study period.

COVID-19 Risk Factors

Rates of COVID-19 were higher among Black patients compared with non-Black patients (13.1% vs 11.5%) and among Hispanic patients compared with non-Hispanic patients (15.6% vs 11.3%). The most prominent differences in rates of COVID-19 were seen between patients with short stays in a nursing home and stays of ≥90 days compared with patients who did not receive care at a nursing home in the year prior to the COVID-19 diagnosis (14.0% and 35.6% vs 10.1%, respectively).

Following adjustment for all other risk factors and compared with no nursing home stay, there was an association between prior short-term stay in a nursing home and a 60% higher hazard for COVID-19 (hazard ratio [HR], 1.60; 95% confidence interval [CI], 1.56-1.65); extended stays were associated with a 448% higher hazard (HR, 4.48; 95% CI, 4.37-4.59). In addition to older age, higher body mass index (BMI), congestive heart failure, inability to ambulate, diabetes, cerebrovascular disease, and higher prevalent comorbidity burden, Black race (HR vs non-Black race, 1.25; 95% CI, 1.23-1.28) and Hispanic ethnicity (HR vs non-Hispanic ethnicity, 1.68; 95% CI, 1.64-1.72) were also associated with higher COVID-19 hazard. Conversely, urban residence, Medicare Advantage coverage, ESKD vintage, cancer, and tobacco use were associated with lower hazards of COVID-19.

National Mortality Trends

Trends in mortality in the period 2013 to 2019 followed a seasonal pattern, with peaks in late January and early February. Beginning in 2020, there were deviations in those trends, commensurate with observed waves of the COVID-19 pandemic. Mortality for Black patients declined in May, returning close to normal historic differences by late summer. Sex differences were variable. Mortality has been high since March 2020; the initial increase was markedly higher in urban areas. The spike in April was driven by key hotspots, particularly New York New York, as well as Detroit, Michigan, and Chicago, Illinois. As COVID-19 became more widespread, the trends shifted.

Postdiagnosis Mortality Risk Factors

Of the 60,090 patients with COVID-19, 26.0% (n=15,612) died, compared with 16.9% of patients without COVID-19 (72,339/438,079), suggesting an association between COVID-19 and higher mortality in the study population. Kaplan-Meier curves for post-COVID-19 survival show attenuated differences in survival between Black and non-Black patients and worse survival outcomes among men and among patients with prior nursing home stays.

Also associated with higher mortality after a COVID-19 diagnosis were age, Hispanic ethnicity, higher BMI, congestive heart failure, and number of prevalent comorbidities. Nursing home residence for 1 to 89 days prior to COVID-19 diagnosis was associated with a 41% higher hazard for mortality (HR vs 0 days, 1.31; 95% CI, 1.25-1.37); extended nursing home stays were associated with a 12% higher hazard for mortality (HR vs 0 days, 1.12; 95% CI, 1.07-1.16).

The hazard for postdiagnosis mortality was 20% higher in men than in women (HR, 1.20; 95% CI, 1.16-1.24). Mortality hazard was lower in Black patients than in non-Black patients (HR, 0.87; 95% CI, 0.84-0.90). There were also associations between home dialysis, longer ESKD vintage, Medicare Advantage coverage, and tobacco use and higher postdiagnosis mortality. Residing in an urban area was associated with lower postdiagnosis mortality.

In citing limitations to the study, the researchers included the difficulty in capturing COVID-19 cases, the short follow-up period, and the possibility that data on all events during the follow-up period were not available at the time of the analysis.

In conclusion, the authors said, “To our knowledge, this cohort study is the first national study using CMS claims data to evaluate COVID-19 outcomes in the Medicare dialysis population using all available 2020 data through December 2020. Our results identified several risk factors for COVID-19 and mortality, which include nursing home residence, race, sex, modality, and several comorbidity conditions, such as diabetes and obesity. There results improve our understanding of COVID-19 and complications in this high-risk population and could inform policy decisions to mitigate the added burden of COVID-19 and death.”

Takeaway Points

  1. Researchers conducted a retrospective, claims-based cohort study to identify risk factors associated with COVID-19 and mortality in Medicare patients undergoing long-term dialysis.
  2. Risk factors for COVID-19 that remained as risk factors for mortality included residence in a nursing home, time on dialysis, obesity, and diabetes.
  3. Also associated with higher mortality after a COVID-19 diagnosis were age, Hispanic ethnicity, higher body mass index, congestive heart failure, and number of prevalent comorbidities.