Chronic kidney disease will be the second leading cause of death in the year 2100.1 The Spanish Registry of Renal Disease (REER) is an essential source of data to know the incidence, prevalence and mortality of patients on renal replacement therapy (RRT) in Spain. The REER is the result of a collaborative effort between the Renal Disease Registries of the Autonomous Communities and Autonomous Cities, the Spanish Society of Nephrology (S.E.N) and the National Transplant Organization (ONT), which is responsible for data management and analysis. In addition to collaborating with the European Renal Association (ERA) and the United States Renal Data System (USRDS) registry, the REER report has been presented at the annual congress of the S.E.N. since 1996 and it is intended that, from now on, it will be published annually in the journal NEFROLOGÍA.

In recent years, nephrology has progressed in the management of chronic kidney disease (CKD), with extensive development and approval of new treatments and diagnostic techniques.2 Despite this, each year a greater number of patients require RRT both in Spain and globally.3 In 2022, the incidence of RRT in Spain was the fifteenth highest in Europe (out of a total of 34).3,4 The prevalence of RRT in Spain was the third highest in Europe (out of a total of 29 European countries reporting data).3,4 In comparison with the United States, incidence and prevalence were substantially better in Spain: 410 patients per million population (pmp) and 2,436 pmp, respectively.5

The aim of this report is to update the data on prevalence, incidence, and mortality of patients with RRT in Spain for the year 2022, comparing the evolution of the situation during the last 10 years

The overall mortality of patients on RRT in the last ten years (2013–2022) has remained stable, between 7.4% and 8.4% (with a slight spike in 2020, probably related to the COVID-19 pandemic). As shown in Fig. 10, the mortality had a minimal increase in patients on PD and renal transplant recipients. Analysis by age group shows an association between RRT modality and mortality, with renal graft recipients being the most protected in all groups, followed by PD patients (with the exception of the >75 years group, in which mortality is equal to HD patients) (Fig. 11).

Fig. 10.

Annual mortality in different modalities of RRT in the period 2013-2022.

DP: peritoneal dialysis; RRT: renal replacement therapy.

Nota: En ingles el signo de decimal es un punto (.) en vez de una coma (,) por favor cambiar “,” por”.”

Hemodialisis:Hemodialysis; DP = PD; Tranplante = Transplant

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Fig. 11.

Annual mortality of patients according to RRT modality and age group in the period 2013-2022.

PD: peritoneal dialysis; RRT: renal replacement therapy.

Nota: En ingles el signo de decimal es un punto (.) en vez de una coma (,) por favor cambiar “,” por”.”

Hemodialisis:Hemodialysis; DP = PD; Tranplante = Transplant

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Of the 6,095 patients on RRT who died in 2022, the most frequent causes of death were infections (27.8%), miscellaneous/other causes (17.2%), myocardial ischemia/cardiac failure (11.7%), unknown (10.3%), tumor (9.6%), and cardiac arrest (8.6%). Fig. 12 shows the distribution of the causes of mortality according to the type of RRT.

Fig. 12.

Distribution of causes of mortality in 2022 according to RRT.

RRT: renal replacement therapy.

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The median overall survival estimate for all episodes since 2004 was 6.2years, with a 95% confidence interval between 6.1 and 6.4. The unadjusted probability of survival is 91, 81, and 57% at 1, 2, and 5 years, respectively.

The adjusted survival analysis is presented in Table 8. The Cox model shows age, diabetes as PRD, being transplanted, sex and the initial modality RRT as independent survival factors, with worse survival for diabetic men, over 45 years of age, who have started RRT with HD and who have not been transplanted (Table 8).

Fig. 13 shows the survival curves of incident patients during the period 2004–2022 based on age group.

Fig. 13.

Adjusted survival curve for incident patients on RRT by age group in the period 2004-2022.

RRT: renal replacement therapy.

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Regarding the survival of kidney transplant patients, in the analysis carried out by ERA-EDTA based on individual data from Spain vs. the global data of participating countries, the data from the 2015–2020 cohort show an age, PRD-and sex-adjusted survival of 98.2% and 97.1% for the first and second years, respectively, for deceased donation, and 99.7% and 99.2% for living donation (Table 7).4

The REER data from the last decade show an increase in the incidence of RRT in Spain between 2013 and 2019, with subsequent stabilization. Kidney transplant activity classifies Spain as a world leader. Furthermore, the mortality stands at 8.4%, a figure that has remained stable in the last 10 years, except with an increase in 2020, attributable to the COVID-19 pandemic.

Slowing the progression of CKD is a medical, social, political and economic challenge that requires global measures. The enormous prevalence of CKD, estimated at more than 15% in our country,8 could affect one in four people by the end of the century.1 The causes the stabilization of the incidence of RRT in the last 4 years should be explored in depth. In 2020 there was a decrease, probably as a consequence of the high mortality of COVID-19 in patients with CKD.9,10 However, in 2021 and 2022, the figures remained at those of 2019. The main possible causes of this stabilization that deserve to be explored are changes in the attitude towards conservative treatment of kidney failure and the effectiveness of new therapeutic tools, without ruling out others reasons. If there were an impact of new treatments, such as sodium-glucose co-transporter type 2 inhibitors (iSGLT2),11,12 future improvements would be expected, since in 2020–2022 the desirable prescription rates had not yet been reached and the effect on progression is greater in less advanced stages of CKD and therefore its full impact will take a few years to be documented.13 Early diagnosis and treatment of kidney failure, as well as earlier referral to Nephrology clinics, could partially alleviate this problem.13–15

With respect to the etiology of CKD, diabetes remains the main cause of the onset on RRT in our country. Although in 2022 this number appear to have decreased compared to the evolution of the last decade, therefore it must be analyzed it with caution. Firstly, because the etiology of kidney disease does not always conform with evident diagnostic criteria; secondly, because 2022 is the first year in which the REER has been adapted to the ERA registry so they became comparable and, therefore, there may be patients classified in another group, and thirdly, because the new category of "lost" occupies 6.8% that previously was not part of the total count (as it was a value that could be left blank). In any case, the approval of drugs that slow the progression of diabetic kidney disease (SGLT2i, finerenone, GLP-1) opens up an optimistic future in this pathology and in CKD, in general.16 The second cause of CKD remains miscellaneous, which in the new classification includes patients whose etiology has not been identified, this is different from the coding prior to year 2022, in which it was reported separately. Although the percentage of cases (21.7%) remains unacceptable, it is expected that the integration of genetics into the CKD diagnostic algorithm will reduce this percentage in subsequent reports.17 Initiatives such as GENSEN, which has identified a probable genetic cause in 25% of young patients (<45 years) with kidney failure of unknown cause in Spain, suggest that more extensive use of genetic diagnosis may help to reduce the percentage of patients with CKD of unknown etiology.18

Spain is a leader in kidney transplantation, with a rate of 71.7 pmp, second only to the United States. Despite an increase in the transplant after donation in asystole, donation after brain death remains the most common, as is the case in the Americas, Europe and Oceania, which are the territories that perform the most transplants globally.19 Compared to the ERA data in its 2022 report, kidney graft survival in Spain is similar to that reported in Europe in the first two years after living and deceased donation.3,4 An effort to increase the rate of transplantation with a living donor in Spain would be desirable given the significant increase in survival (graft and patient) that this modality offers as compared to transplantation from a deceased donor.

In general terms, and ignoring the impact of COVID-19,20 mortality in patients on RRT remains stable, without decreasing, partly as a consequence of an ageing population, but also due to the systematic exclusion of such patients in clinical trials. There are few studies that allow the inclusion of patients with an estimated glomerular filtration rate of less than 30 ml/min/1.73 m2, so the indication of practically all drugs affecting prognosis is very limited in the HD and PD population.21 While it is true that off-label use is widespread in certain circumstances, we do not even have real-life data to support the prescription of drugs such as SGLT2i, neprilysin antagonists, mineralocorticoid receptor antagonists or even renin-angiotensin-aldosterone system blockers. A similar situation occurs with patients with a kidney graft, rarely included in clinical trials.

As shown in Table 7, graft and transplant patient survival in Spain is comparable to that published by ERA. However, it is worrying that the 2020 mortality peak, clearly related to COVID-19, has not returned to previous values, as occurred in HD patients, but remains high and is even increasing. A detailed characterization of the causes of death in this particular population may help reverse this worrying recent trend.10

The present report has limitations. First, registries may inherently lead to the loss of some non-mandatory data. However, the fact that they are mandatory means that these losses are not relevant in the overall analysis. In addition, the prevalence and incidence data are real, since these two indicators are compulsory. Second, the change in the classification of etiology makes it difficult to compare data prior to 2022, especially in the categories of losses, others and miscellaneous. In this regard, the etiology of CKD may have some biases due to the absence of well-established diagnostic criteria (for example, vascular or diabetic). Third, the incidence and prevalence rates have not been standardised by age and sex, which could have implications when analyzing the data by CCAA. Finally, the causes of mortality are not always very obvious, so there could be some patients with an erroneous diagnosis.

The REER analysis of the last decade shows that the incidence of people requiring RRT in Spain increased until 2019 and seems to have stabilized since then. However, some differences between autonomous communities may persist, the causes of such differences should be studied in depth in order to optimize the management of kidney disease taking into account the different sociodemographic factors. Diabetes remains the leading cause of CKD requiring RRT in Spain. Age, modality, sex and diabetes are independent predictors of mortality in patients requiring RRT in Spain.

The Spanish Registry of Renal Patients (REER) will be named the Spanish Registry of Dialysis and Transplantation (REDYT).

The research of AO, BQ, ES, AM, DH is funded by the Carlos III Health Institute (ISCIII) FIS/FEDER Funds RICORS program to RICORS2040 (RD21/0005/0001) funded by European Union-NextGeneration EU, Mechanism of Recovery and Resilience Facility (MRR) and PREVENTCKD Consortium Project ID: 101101220 Programme: EU4H DG/Agency: HADEA. MM's research is funded by the Instituto de Salud Carlos III (ISCIII) FIS PI23/01518