Almost 3 million people worldwide receive haemodialysis treatment every year, and this number is expected to double by the year 2030(1). More than half of all haemodialysis patients are elderly (aged ≥65 years) (1). For this population, well-timed placement of an arteriovenous (AV) vascular access by AV graft (AVG) or AV fistula (AVF) may limit the usage of a tunnelled central venous catheter (CVC) (2). This is important as a well-timed placement of AV access in elderly haemodialysis patients may reduce the risk of complications, such as infection and thrombosis, that are associated with prolonged use of tunnelled CVCs, thereby improving the quality of care and overall prognosis of the patient (2). Currently, the general guidelines for selecting a dialysis vascular access include a categorized preference order, where AVF, AVG and CVC are the first, second and last choice, respectively (3). AVFs are often selected as the first choice due to their longer patency and lower infection rates. However, AVF maturation process can be slow and unpredictable, posing unique challenges for elderly patients. On the other hand, AVGs, while quicker to mature, are traditionally associated with a higher rate of complications, which often makes them a less preferred method of dialysis vascular access (3).

This categorized preference order for the placement of vascular access has become a major point of debate worldwide (4,5). For decades, AVF placement was considered a preferred method of choice for the majority of patients that required haemodialysis for treating end-stage kidney disease (ESKD). However, recent advances in the treatment of ESKD led to the changes in the incidence and prevalence of patients with advanced renal conditions (6). Changes in the treatment of ESKD have also changed our understanding of the pros and cons associated with different vascular access options. With increasing complexity of the health profiles of patients, particularly among elderly populations, it is necessary to reassess the efficacy and safety of AVGs and AVFs.

Haemodialysis is now offered to elderly ESKD patients with various comorbidities, such as diabetes mellitus, hypertension, cardiovascular disease, chronic respiratory conditions, osteoporosis, and autoimmune disorders such as lupus. Age is a major biological variable that can affect the outcomes of vascular access (7). The optimal vascular access (VA) strategy in elderly dialysis patients is still unclear due to their shorter life expectancy, difficulties in VA maturation and significantly higher risk of primary AVF failure compared to younger adults (8). Recent studies in elderly patients suggest that AVF may not demonstrate clear advantage over AVG in terms of patency. Therefore, patients can still benefit from AVG, as it is associated with a shorter time to maturation (9-11). To the best of our knowledge, there are no reviews that pool data on the difference in outcomes, such as overall survival, mortality rates, access survival, primary patency, maturation failure and risk of infection in elderly patients. The goal of the present study is to summarize data from individual studies to compare the outcomes of AVG versus AVF for haemodialysis access in elderly patients.

Eligibility criteria

Study design. Randomized controlled trials/non-randomized trials/cross-sectional/cohort/case-control studies were included if they satisfied the inclusion criteria listed below.

Study participants. Studies containing data of elderly patients (≥60 years) requiring haemodialysis access were incorporated.

Exposure. Studies evaluating the difference in outcomes between AVF and AVG access for elderly patients were included.

Outcomes. Studies reporting any of the following outcomes: Overall survival/mortality rates, access survival, primary patency, maturation failure and infection, were eligible for inclusion.

Exclusion criteria. Case reports, case series, conference abstracts, letters to editors, commentaries and studies not reporting any of the aforementioned outcomes were excluded from the analysis.

The current recommended guidelines for vascular access do not provide any specific age-based recommendations for the preferred placement of AVF over the AVG (3). Elderly patients undergoing haemodialysis present unique challenges, such as diminished vein and elasticity, high prevalence of atherosclerosis, increased risk of infection and comorbidities, for the establishment and usage of the vascular access (4). The present systematic review assessed the risk of survival outcomes associated with AVG and AVF access for haemodialysis among elderly patients.

The present study investigated 12 studies that fulfilled the eligibility criteria. The majority of these studies were conducted in the USA followed by South Korea and China. Almost all the studies [except for Murea et al (17) and Robinson et al (18)] were retrospective, and the majority of them were of poorer quality with a high risk of bias. It was revealed that AVG was associated with significantly higher risk of mortality, lower access survival and higher rate of infection. At the same time, AVG access in these patients correlated with significantly lower risk of maturation failure. Though subgroup analysis was not possible due to limited number of studies for each outcome, there was some variation in the individual study estimates based on the age cut-off, with higher magnitude of association in higher-age group of patients. Sensitivity analysis did not reveal significant effect of any single study on the magnitude or direction of association.

These results were further confirmed by using adjusted HR for the pooling of effect size. The crude estimates are prone for confounding as they are not adjusted for any important risk factors. The use of adjusted HR takes into account these relevant confounding factors, and thus provides more reliable estimate of the differences between the two vascular access methods in elderly patients. While there are no existing reviews to compare the observations of the present study in an elderly age group, the current results were in agreement with the reviews that focused on adult patients and compared AVG and AVF for haemodialysis access (26-28). A possible explanation for the observed differences in the outcomes between these two haemodialysis access types may be due to a higher rate of infections as a result of the colonization of the foreign materials within the vascular space by skin microorganisms. This may lead to poor overall survival and access survival in patients undergoing AVG for haemodialysis access (26).

The increased mortality rate associated with AVG when compared with AVF in the elderly population cannot be solely attributed to the choice of vascular access. It is important to consider that the selection between AVG and AVF is typically dictated by patient-specific factors such as vascular health, comorbidities, and the overall clinical profile of the patient (4). This introduces an inherent selection bias that may lead to worse outcomes in patients approved for AVG.

An important finding of the present study is the higher rate of infection in patients with AVG. However, the present analysis did not distinguish between infections at the access site and systemic events, nor was the severity of these infections graded. Future studies should consider investigating these aspects in more detail, as the type and severity of infection could influence the decision-making process regarding the choice of access type.

AVFs have a significantly higher risk of the maturation failure, often requiring various intercurrent guidelines strongly recommend AVF as a first-line and optimal vascular access method for haemodialysis. There is insufficient information available for evaluating the qualities of this methods (29). Since AVF is associated with higher maturation failure and frequently requires repetitive interventions, its indiscriminate use might result in the ineffective usage of the services and resources (29).

The major strength of the present review was the rigorous methodology and comprehensive literature search that adds to the limited evidence available on the comparison these two methods of vascular access. The present study did not detect any significant changes in the effect size, as indicated by the sensitivity analysis. This further enhanced the credibility of these results. However, there are some limitations in the current study. Substantial between-study variability was found for most of the outcomes. The majority of the studies were of poorer quality and limited heterogeneity. This might affect the external validity (generalisability) of the findings. In addition, publication bias was unable to be assessed due to the small number of studies, which further limits the credibility of the evidence. The retrospective nature of the included studies made it challenging to establish the causal association. Hence, longitudinal evidence is required for the identification of reliable effect size. This will allow making evidence-based recommendations for deciding on the appropriate vascular access type for elderly haemodialysis patients at the hospital setting. Finally, the results of the present review may not be credible as nine out of the 12 studies had high-risk of bias. Given these limitations, it is crucial to stress that the present results should not be interpreted as definitive evidence for the decision-making in the clinical setting. The small number and the retrospective design of most of the included studies, and other potential biases restrict us from deriving firm evidence-based recommendations from this meta-analysis.

Nevertheless, the present study had certain important implications for the healthcare professionals treating elderly haemodialysis patients. A stronger association of survival outcomes was revealed with AVG compared with AVF in elderly patients. However, the maturation failure was higher with AVF and limited evidence was available in terms of RCTs. The potential confounding effect of infections on survival analyses was also notable. Although the meta-analysis showed a worse survival rate with AVG, whether this was influenced by the increased rate of infections in this group was not specifically investigated. Thus, the impact of infections on survival outcomes remains unclear. In the future, more rigorous statistical methods may be necessary to control for such confounding factors and accurately determine the individual effects of AVG and AVF on survival rates in the elderly.

While the current analysis revealed a stronger association of survival outcomes with AVG compared with AVF in elderly patients, a higher maturation failure rate was observed with AVF. The limited availability of RCTs evidence restricted the current study from deriving firm evidence-based recommendations from the results. However, importantly, the KDOQI guidelines recommend basing the decision on vascular access not only on the age of the patient or access type but to follow a comprehensive, individualized life plan that takes into consideration the history of the patient, comorbidities, vascular health, life expectancy and future needs. These guidelines should be considered when deciding on the appropriate access type for each elderly haemodialysis patient.