The corona virus disease 2019 (COVID-19) was first recognized in December 2019 in Wuhan, China [1]. Owing to the surge in COVID-19 infections worldwide, many hospitals were forced to go into emergency mode, and this has prevented them from treating chronically ill patients and performing various procedures and surgeries in a timely manner. In this context, the significance of kidney replacement therapy (KRT) cannot be overstated. KRT is essential for sustaining life and must be provided at appropriate times. However, the COVID-19 pandemic has necessitated the adoption of changes in the methods and timing of administering KRT to patients.

Individuals with chronic kidney disease, especially those in the advanced stages, such as end-stage kidney disease (ESKD), have weakened immune systems and are at a higher risk of infection, including viral infections like COVID-19 [2]. Notably, patients undergoing KRT, including maintenance dialysis or kidney transplant (KT) cases, are particularly vulnerable to COVID-19 [3–5]. Patients in need of KRT, particularly those undergoing hemodialysis (HD) and attending the dialysis center three times a week, face an elevated risk of contracting COVID-19 owing to their heightened exposure to healthcare facilities. Although several studies have reported on this concern [6], there is a scarcity of domestic research on this issue, necessitating an in-depth exploration.

We aimed to analyze data from the nationwide claims data in Korea to investigate the differences in ESKD incidence and changes in KRT modalities during the COVID-19 pandemic and compare these to the previous period. This study sought to determine whether COVID-19 has affected the incidence, choice of modality, and length of stay (LOS) of patients with ESKD, and whether this varied by hospital system. The acquisition of comprehensive epidemiological data on this concern would be instrumental in developing response strategies for the management of patients with ESKD in the face of future pandemics or similar infectious disease outbreaks.

From 2018 to April 2022, the annual incident cases of ESKD in South Korea remained stable, ranging from 15,338 to 15,833 per year, with no significant differences in the absolute numbers before or after the pandemic. However, there were significant shift in the distribution of KRT modalities among the patients with incident ESKD. The percentage of patients with PD decreased from 5.7% in 2018 to 1.3% by 2022. The proportion of HD patients undergoing HD increased from 81.6% to 85.0%, but the number of patients using catheters at the initiation of HD decreased from 63.6% to 55.4%. The proportion of KT recipients remained relatively stable, ranging from 12.7% to 17.3%. However, the preemptive KT percentage decreased from 50.8% to 44.6% (Table 1).

When examining the characteristics of incident ESKD patients, age, sex, insurance type, or other factors not significantly changed before and after the pandemic. The average age ranged from 63.3 to 64.7 years over the five-year study period, with a male predominance of over 60%. An important observation we made involved the remarkably high proportion of medical aid beneficiaries, ranging from 11.9% to 13.2%. In South Korea, medical aid beneficiaries constitute only 3% of the population [12], making this ratio notably high among patients with ESKD. Approximately 70% of the patients had diabetes, and one in three patients had conditions such as congestive heart failure or peptic ulcers. When assessing comorbid conditions within the year preceding the ESKD diagnosis, the Charlson Comorbidity Index (CCI) score [13] ranged between 5.4 and 5.8 points (Table 1).

This study aimed to investigate the incidence of ESKD, modalities of KRT, and changes in healthcare access for ESKD patients in South Korea during COVID-19 pandemic.

Initially, our findings revealed that the absolute number of annual incident cases of ESKD in South Korea remained stable from 2018 to April 2022, ranging between 15,338/ year to 15,833/year. Even when divided by quarters from 2018 onwards, there was no statistically significant change in the incidence of ESKD. The ITS analysis confirmed that the pandemic had no immediate or long-term impact on the overall KRT incidence. This stability in ESKD incidence may reflect the resilience of the healthcare system in continuing to diagnose and manage ESKD cases despite the challenges posed by the pandemic.

Potential factors that could influence the incidence of ESKD include acute kidney injury (AKI), which frequently occurs in individuals diagnosed with COVID-19, especially among those who are hospitalized, leading to a heightened incidence of AKI overall. Studies have shown an increased risk of developing CKD in COVID-19 patients, with many AKI survivors progressing to CKD within 90 days, and some potentially advancing to ESKD [14]. The occurrence of COVID-19-associated AKI or AKI on CKD during the pandemic might have impacted the incidence of ESKD. A notable decline in incident ESKD cases was observed in the United States early in the pandemic, attributed to increased mortality in patients with advanced CKD and compromised access to KRT preparations [15]. Similarly, the possibility remains that the incidence of ESKD in Korea might have been affected by COVID-19-related premature death in CKD patients.

Contrary to the stability of the ESKD incidence rate, there were notable changes in the distribution of KRT modalities among patients with incident ESKD during this period. Specifically, the percentage of patients undergoing PD decreased from 5.7% in 2018 to 1.3% by 2022. In contrast, the proportion of patients receiving HD increased from 81.6% to 85.0%. This change in the distribution of KRT modalities is speculated to be a continuation of the change in treatment trends for patients with ESKD in Korea, as reported in several previous studies [16], rather than a direct consequence of the COVID-19 pandemic. As seen in the ITS analysis, previously on a decreasing trajectory, the PD incidence rate continued to decline, but have slowed. In addition, the proportion of patients in whom HD was initiated with catheters decreased from 63.6% to 55.4%. This observation indicated that a greater number of patients started HD through established vascular access rather than through emergent catheter insertion, implying that high-quality medical care was provided even during the coronavirus pandemic.

The proportion of KT recipients remained relatively stable, ranging from 12.7% to 17.3%. However, the preemptive KT rate decreased from 50.8% to 44.6%. This decline is hypothesized to be due to the timing of transplant surgery that may have been affected by difficulties and disruptions in healthcare during the pandemic. Additionally, KT may have been performed with caution because a high dose of immunosuppressant is required in the early stages of transplantation. When considering the long-term benefits of KT over chronic dialysis [17], this highlights the need for a robust and adaptable transplant infrastructure that can navigate the complexities of infectious disease outbreaks while continuing to provide transplant procedures safely.

During the COVID-19 pandemic, significant changes in healthcare access and patient behavior were reflected in the variations in CCI scores observed among ESKD patients from 2018 to 2022. The comorbidity score of ESKD patients gradually decreased from 5.8 to 5.4. Among the 15 conditions examined, myocardial infarction, congestive heart failure, DM, DM complications, and paraplegia all decreased slightly during pandemic and chronic pulmonary disease had the greatest impact on the CCI score, decreasing sharply from 45.2% in 2018 to 31.0% in 2022. The decrease may be partly attributed to the reduced frequency of routine healthcare visits during the pandemic, impacting the management and diagnosis rates of conditions such as DM complications and congestive heart failure. Furthermore, specific public health measures, such as lockdowns reducing physical activity, alongside changes in patient behavior–including increased use of masks and social distancing–likely contributed to the observed decrease in chronic pulmonary disease prevalence [18].

This study investigated the ESKD incidence rates by KRT modality and age. ITS analysis revealed that no immediate change was observed in any KRT modality or age group following the COVID outbreak. Age-specific analysis revealed that higher age groups had higher incidence rates of ESKD, with the elderly population, particularly those aged 75 and older, experiencing notably higher rates. This finding is consistent with the well-established association between aging and the risk of ESKD [19]. The incidence of ESKD in children under 18 decreased before COVID-19, but no significant trend was observed after COVID-19. Chronic kidney disease in children under 18 is mainly associated with congenital factors such as congenital kidney malformations and congenital urinary tract disorders [20]. During the COVID-19 era, it is plausible that factors such as psychological stress could have exerted a negative effect on fetal health, thereby potentially contributing to the absence of a decline in ESKD incidence among children under 18. Additionally, due to the significantly lower incidence of ESKD in children compared to other age groups, it’s impossible to entirely rule out the possibility of error. Contrary to those under 18, older adults aged 65 and older exhibited a tendency of increasing ESKD incidence before the onset of COVID-19. They are more vulnerable to ESKD due to age-related weakening of kidney health, making those with pre-existing conditions such as hypertension and diabetes more susceptible to ESKD [9]. However, there was a tendency for the incidence of ESKD to decrease among the 45–64 age group and the 65–74 age group. The lack of such trends during the COVID-19 era may be attributed to the development of new treatments delaying the progression to ESKD (such as SGLT-2 inhibitors, GLP-1 agonist, RAAS blockers, etc) or changes in healthcare utilization patterns during the pandemic [21]. It is also possible that there was an underestimation of ESKD due to deaths occurring before reaching KRT. As previous data [22], during the COVID-19 pandemic, there were more excess deaths observed in the age groups of ‘50–64’ and ‘65–79’ compared to those aged ‘80 and older’ when compared to the previous years.

We investigated whether the COVID-19 pandemic caused difficulties in hospitalization or led to situations where the necessary medical care was not provided. There were no significant changes in hospitalization-related medical care for PD or KT recipients before and after COVID-19. Only patients undergoing HD showed a tendency for reduced hospitalization and LOS, reflecting potential changes in patient care patterns during the pandemic. While a decrease in hospitalization may, in some instances, be seen as a positive outcome indicative of outpatient management or improved disease management, but their potential impact needs to be examined more carefully. During the COVID-19 pandemic, there was a widespread culture of reluctance to visit and admit hospitals due to concerns about infection, and the provision of medical services was very different from the time when there were no infectious diseases. Despite the fact many patients receiving HD are admitted to nursing hospitals under special circumstance, there continues to be a decrease in both LOS and the number of admissions.

Although informative, this study had some limitations. First, there may have been minor errors in the number of people infected with COVID-19. Patients who could not be traced in claims data owing to data privacy concerns were excluded from the study. Cases that could not be traced in the claims data were as follows. First, if hospitals had treated fewer than three COVID-19 patients during the entire study period, these patients were excluded. Second, patients infected with COVID-19 between January and March 2020 were excluded from the study. However, it is important to note that during January to March 2020, the early stages of the COVID-19 outbreak, the number of COVID-19 cases was extremely low. Although there may have been variations in patient numbers, the patients included in this study adequately represented the overall population of patients who underwent KRT. Second, it was not possible to distinguish between living and deceased donor KT based on claims data alone. However, all preemptive KT cases were probably living donor cases, and there appeared to be no significant change in either total or preemptive KT before and after the COVID pandemic. Third, we could only access the claims data until June 2022. This limited timeframe may have affected the comprehensiveness of our findings. This constrained timeframe restricted our analysis to a specific period, potentially limiting the depth and breadth of insights obtained from a more extended dataset. Future research extending beyond this period is crucial to capture the evolving dynamics and potential long-term consequences of the observed shifts in ESKD and KRT patterns.

This study provides valuable insights into the dynamics of ESKD and KRT during the COVID-19 pandemic in South Korea. These findings highlight the stability of ESKD incidence while revealing shifts in the choice of KRT modalities, with a notable increase in HD utilization. While there have been individualistic differences as COVID-19 has impacted everyone, this study showed that the overall healthcare system remained stable during the pandemic, with no major disruptions to care for patients with ESKD in South Korea. As we navigate the complexities of future infectious disease outbreaks, these insights serve as a foundation for informed strategies to safeguard the well-being of patients with ESKD.