Background
Chronic kidney disease (CKD) is a major public health issue with an increasing number of patients treated worldwide [
1]. Although hemodialysis (HD) three times per week is the most frequent renal replacement therapy [
2], HD regimens have been modified to improve the patients’ quality of life and biological parameters [
3‐
7]. Increasing HD weekly frequency is considered to be the best way to mimic the kidney functional role [
8‐
10]. Several studies have reported that daily HD (DHD) improves hypertension [
3,
11,
12] and uremia [
4,
8] management in addition to ventricular hypertrophy [
8,
12,
13].
In France, the Renal Epidemiological and Information Network (REIN) registry collects data on all patients who start renal replacement therapy in the entire country [
14]. Analysis of the REIN data highlighted the clinical feature heterogeneity of patients starting DHD (i.e., 5 or 6 HD sessions/week) [
15], and showed that the risk of death is higher in patients on DHD than in matched patients on HD 3 times/week [
16]. This confirmed a previous study by Suri et al. that included patients undergoing in-center HD [
17]. Conversely, other studies reported that DHD is associated with better survival [
18‐
23]. These contradictory results could be explained by differences in the practices associated with DHD between France and other countries [
16,
17].
The Australian and New Zealand Dialysis and Transplant Registry (ANZDATA) has been collecting data on all patients undergoing dialysis and kidney transplantation in Australia and New Zealand for over 40 years. Analysis of ANZDATA data showed that intensive HD is used in both countries, and that various regimens (long nocturnal, short DHD) have been developed mainly for home dialysis [
24,
25]. Particularly, long nocturnal DHD and home conventional HD have been implemented since 2001 [
26,
27]. Since then, several reviews [
25,
26,
28] described the benefits of nocturnal DHD on biological functions and quality of life. A recent study showed (in some analyses) lower mortality with intensive HD, compared with conventional HD [
24] in Australia and New Zealand.
As the REIN and ANZDATA registries collect similar data, we decided to compare the characteristics, care trajectories, survival and access to renal transplantation of French and Australian/New Zealand patients undergoing DHD to highlight possible differences.
Discussion
This is the first study that describes and compares the characteristics and estimated survival rates of all incident patients treated at least once with DHD during their care trajectories in Australia/New Zealand and France between 2003 and 2012.
France, Australia and New Zealand are very different countries with specific lifestyles, healthcare systems, and disease/comorbidity prevalence. France is a democratic republic with centralized, universal health coverage: the national health insurance system covers the entire population. Australia and New Zealand also have national health insurance schemes that provide universal coverage, including access to dialysis treatment. Australia has a federal government where the healthcare system is divided across levels of government. In all three countries, population is ageing. As a consequence, prevalence of chronic diseases, such as CKD, is increasing. In 2013, the overall incidence of renal replacement therapy was 160 per million population (pmp), 110 pmp, and 123 pmp in France [
30], Australia, and New Zealand [
31], respectively. The REIN and ANZDATA registries have been established in these countries to monitor the incidence, prevalence and outcomes associated with end-stage renal disease (ESRD). Although the REIN registry is much younger than the ANZDATA registry, they collect similar types of data and have the same objectives. Therefore, their data could be used to study and compare DHD practices in Australia/New Zealand and France.
This study shows that patients who started DHD in Australia and New Zealand between 2003 and 2012 were younger, with high BMI, and mainly cardiovascular comorbidities. Conversely, in France, they were older, with less comorbidities but died rapidly. Moreover, in all three countries, DHD modalities were not widely established during the study time. Indeed, the percentage of incident patients on DHD during the study period was very low (~ 1% in France and ~ 2% in Australia/New Zealand). Differently from the United States and Canada where DHD has been used for a long time [
3,
4,
21], in France, knowledge about DHD practices was poor before 2016. In Australia and New Zealand, Marshall et al., evaluated frequent/extended dialysis modalities, but did not specifically study short DHD [
24,
32]. The costs and constraints of in-center DHD are higher than those of PD or HD 3 times/week [
3,
33]. These facts could limit in-center DHD prescription by nephrologists and its acceptance by patients, and could also explain why DHD was not much implemented in France, Australia and New Zealand during the study period. However, the new low-flow DHD modality at home is slowly progressing in France since 2012, and practices associated with frequent HD might change in the future, at least in France [
33,
34].
Despite the infrequent DHD use in all three countries, we observed several country-specific differences in terms of DHD practices. In our previous studies on French patients, we reported the heterogeneity of clinical features and care trajectories of patients on DHD (15,16). In agreement, in the present French cohort, patients on early DHD were very different from patients on late DHD. Overall, French patients on early DHD were older and with several comorbidities, although we previously identified also a subgroup of young patients with high access to renal transplantation [
16]. Therefore, in France, DHD is mainly used by two groups: 1) older and frail patients, presumably in response to cardiac instability and comorbidities, and 2) young patients to maintain their quality of life before kidney transplantation [
15,
16]. Conversely, in the Australia/New Zealand cohort, patients on early DHD and late DHD were comparable. Overall, Australian/New Zealand patients were younger, with more comorbidities than the French ones. Nevertheless, a similar distinction between old and young subgroups of patients on DHD could be made also in Australia and New Zealand.
Besides the patients’ profile differences, we also observed differences in care trajectories for patients on DHD. First, among Australian/New Zealand patients on late DHD, a high proportion had PD as first dialysis modality (12% vs 6.5% in France). PD was very common in Australia and New Zealand before 2000 (more than 30% of dialyzed patients on PD, mainly at home) [
27,
35]. After 2000, long nocturnal HD and home HD have been progressively put in place [
27,
35]. Accordingly, 20.8 and 3% of patients on DHD in Australia/New Zealand and in France, respectively, underwent long nocturnal DHD. In France, home HD and nocturnal HD were very rare until 2012, probably because of the many care facilities (in center, satellite units) that can cover the patients’ demand in the entire country [
36] and the smaller home-facility distance compared with Australia and New Zealand.
On the other hand, the care trajectories after DHD initiation were comparable in the three countries. Among patients still alive at the endpoint, a similar proportion of patients in Australia/New Zealand and in France were still on dialysis (HD < 5 sessions/week or DHD; Fig.
1).
Despite differences in clinical features (less comorbidities in the French group), the mortality risk and access to kidney transplantation were comparable in Australia/New Zealand and France in the matched population. The characteristics of patients who underwent kidney transplantation also were comparable, suggesting similar selection criteria in these three countries. We hypothesized that survival rate might be higher among Australian/New Zealand patients than among French patients with ESRD on dialysis. Based on ANZDATA annual report (2013), the mortality rate per 100 patient-years was 13.1 (95%CI: 12.5–13.8) for dialysis-dependent patients in Australia and 13.7 (12.3–15.2) in New Zealand [
37]. In France, the one-year survival was 83.2% (95%CI: 82.9–83.5) for the 2002–2013 incident patients [
38]. We could not compare survival of patients with ESRD in the three countries because in the national annual reports, for survival analyses, transplanted patients were censored in the ANZDATA [
37], but not in the REIN registry [
38]. Survival rate might not be the best way to highlight the benefits associated with DHD, thus explaining the contradictory results of previous studies [
16‐
23]. Alternatively, the analysis of the patients’ quality of life could help, but this information is not routinely collected in registries.
The major strength of our study is that this is the first comparison of DHD associated practices in France and Australia/New Zealand. Furthermore, thanks to the REIN and ANZDATA registries, we could include a large population-based cohort on DHD between 2003 and 2012 and we could take into account various clinical characteristics.
Our study has several limitations. The medical reasons explaining the nephrologist’s decisions to start or to switch to DHD were not recorded in the REIN and ANZDATA registries, raising the possibility of selection bias. Differently from the REIN registry where data are collected at renal replacement therapy initiation, at every dialysis modality change, at death, at renal transplantation and also annually, ANZDATA collects data only annually. Therefore, the dates of dialysis initiation, DHD initiation, death and renal transplantation are registered in ANZDATA at the survey update, and the follow-up times calculated for the Australian/New-Zealand cohort were less consistent. The study design allowed us to analyze the global survival of patients who started DHD between 2003 and 2012 in Australia/New Zealand and France, but not the survival specifically for the period they underwent DHD. Indeed, we could not identify the exact duration of DHD treatment for each included patient. Finally, we could study only the data collected in both registries; for example, we did not have any information on the patients’ income or quality of life.