Long-term outcomes of COVID-19 in patients receiving maintenance dialysis: a propensity score matched population-based cohort study

Background — There is concern regarding the long-term impact of COVID-19 on the maintenance dialysis population. This study describes the long-term morbidity and mortality of COVID-19 among patients receiving maintenance dialysis in comparison to uninfected controls.

Methods — We conducted a population-based cohort study of patients receiving maintenance dialysis in Ontario, Canada, between March 14, 2020, and December 1, 2021 (pre-Omicron), with follow-up until March 31, 2023. We accounted for confounding using propensity-scores to match each patient with COVID-19 to four uninfected controls. The primary outcome was all-cause mortality, while secondary outcomes included subsequent COVID-19 infection, COVID-19 associated death, composite of cardiovascular (CV)-related death or hospitalization, all-cause hospitalization, and admission to long-term care, or complex continuing care.

Results — Our matched cohort included 3,340 maintenance dialysis patients: 668 with COVID-19 and 2,672 controls. Over a median of 1.8 years of follow-up, the rate of long-term all-cause mortality for 90-day COVID-19 survivors was 11.9 deaths per 100 person-years which did not differ from 13.9 deaths per 100 person-years in those without COVID-19 infection; hazard ratio (HR) 0.86, (95% CI 0.72 to 1.03). Similarly, no significant difference was observed on a composite outcome of cardiovascular death or hospitalization, all-cause hospitalization, long-term care or complex continuing care placement. Prior COVID-19 infection was associated with a reduced risk of subsequent COVID-19 infection (HR 0.75; 95% CI 0.63 to 0.88). Subsequent COVID-19 infection was associated with a higher rate of death (HR 1.68; 95% CI 1.42 to 1.98).

Conclusions — Individuals receiving maintenance dialysis who survived their initial COVID-19 infection did not have an increased long-term risk of death, all-cause hospitalization, or cardiovascular disease compared to those without COVID-19. Subsequent COVID-19 infection during follow-up, however, was associated with increased mortality.