Predialysis nephrology care and dialysis-related health outcomes among older adults initiating dialysis

In older adults treated with chronic dialysis, greater intensity of predialysis nephrology care was associated with more favorable health parameters and outcomes at the time of dialysis initiation and for the first two years following initiation. A greater number of predialysis visits were independently associated with a lesser likelihood of having a very low eGFR and severe anemia and a greater risk of permanent vascular access and use of peritoneal dialysis at dialysis initiation. Moreover, a higher number of predialysis visits was associated with decreased risk of death and higher chance of kidney transplantation during follow up. Results were consistent in subgroup analyses among very older adults, those with a substantial burden of comorbidity, and those whose initial visit occurred 3 months before dialysis initiation.

In contrast to most prior studies of predialysis nephrology care, which focused only on mortality after dialysis initiation, we evaluated outcomes at dialysis initiation (e.g., placement of permanent vascular access, presence of severe anemia, use of peritoneal dialysis) in older patients, finding that nearly all were more favorable with more frequent predialysis nephrology care. These results raise the question of whether improving the frequency of predialysis care for older patients with kidney disease represents an opportunity to improve preparation, treatment of complications, and modality selection for chronic dialysis. Cohort studies in the United States and Europe have reported that 50 % of incident older dialysis patients begin dialysis with a catheter instead of arteriovenous graft or fistula (i.e., permanent vascular access), and that catheter use is associated with up to a 70 % increase in death at 1-year among these older dialysis patients [32, 33]. Comparable to our results, Avorn et al. found that more frequent predialysis nephrology care (?3 visits) was independently associated with a 1.5 fold increase in permanent vascular access in a mixed Medicaid and Medicare cohort [8]. Similarly, many older Medicare recipients initiate dialysis with a hemoglobin 9 g/dL, despite current guideline recommendations [34]. Severe anemia, as defined in this study by a hemoglobin??9 g/dL, has also been observed to be independently associated with the additional burden of transfusions [35]. Peritoneal dialysis appears to be underutilized in older adults, despite the observation that many older patients do not cope well with in-center hemodialysis [36]. A recent literature review concluded that most older patients have the requisite physical and cognitive skills to successfully perform peritoneal dialysis, and have excellent compliance and success with this modality [37]. In addition to similar survival compared with similar aged individuals on hemodialysis, older patients treated with peritoneal dialysis may have better quality of life [37, 38].

We are not aware of prior studies reporting the relationship between frequency of predialysis nephrology and access to kidney transplantation in older adults. Although overall rates of kidney transplantation were low, we did observe higher rates of kidney transplantation in patients who received more intensive nephrology care. While kidney transplantation is less common in older compared with younger patients with ESKD, a steady increase in kidney transplantation in older adults has been observed during the last decade [39, 40]. Similar to their younger counterparts, older patients who undergo transplantation have lower mortality rates and higher quality of life compared with those receiving chronic dialysis [39, 40].

Our results reporting lower 2-year mortality among older patients who received more frequent predialysis nephrology care are broadly consistent with prior studies. In three large cohort studies of older Medicare recipients, infrequent (5 visits before dialysis initiation) or late (3 months of care before dialysis initiation) nephrology care was independently associated with up to a 36 % increase in 1-year mortality [5, 6, 9]. In a recent examination of secular trends in timing of nephrology care for older Medicare patients, a large increase in timely nephrology referral prior to dialysis was observed, and referral to a nephrologist was associated with lower mortality. Although there was only a very modest improvement in patient survival over this time period, more timely referral to a nephrologist appeared to account for about half of this improvement [9, 41]. In a German study comparing 1-year mortality in adults with pre-ESKD who were??=75 years with those 75 years, late nephrology referral (8 weeks before starting dialysis) was similarly associated with an increased risk of mortality in both older and young adults [32].

We are not advocating broad nephrology referral for all older patients with severe CKD. Decisions regarding implementing guideline recommendations and dialysis preparations for older patients are often particularly complex and challenging because of the burden of disability and functional compromise [42–45]. Although members of this cohort who received more frequent predialysis nephrology care experienced more favorable outcomes, it is important to note that our study was restricted to those who initiated chronic dialysis. Since many older patients have slow progressive loss of kidney function and die before progressing to dialysis initiation [46], predicting prospectively which ones will start chronic dialysis among large populations of older adults with severe CKD can be challenging and balancing the risks and benefits of relevant management strategies (e.g., permanent vascular access surgery) may not be straightforward [47]. A recent small study testing clinical vignettes of older patients with severe CKD among healthcare providers noted that providers would only refer 50 % of these patients to a nephrologist [48]. Both physician specialty (e.g., internist, geriatrician) and patient characteristics such as comorbidity burden, cognitive decline, and functional impairment were noted to influence referral decisions [48]. While we did not have data regarding important clinical attributes such as frailty and dementia, we did observe an association of improved dialysis-related outcomes with predialysis nephrology care even in patients with the highest degree of comorbid disease burden and advanced age. Clearly, a nuanced patient-centered approach is needed for decisions regarding nephrology referral for older adults with severe CKD.

There are limitations to this study. First, selection bias could impact our findings because predialysis nephrology care was allocated in a nonrandom manner and some characteristics differed between these groups. Patients with more rapid loss of kidney function might be both more ill and less likely to see a nephrologist. However, we included a robust number of important covariates that could have potentially confounded our results and employed a weighted propensity score approach to minimize this concern [19]. Second, lead time bias could affect our findings because patients with higher intensity nephrology care initiated dialysis at higher eGFR values, and may possibly have less severe disease. However, the relationship between intensity of predialysis nephrology care and outcomes was unchanged across strata of eGFR. Third, although the time period of this study and its data are from 2000 to 2002 and may not reflect current rates of nephrology referral for older adults, nephrology referral guidelines for patients with severe CKD have not changed since the conduct of this study; therefore, these findings remain relevant. Fourth, because all participants in this cohort initiated dialysis, we cannot comment on the impact of predialysis nephrology care on outcomes in older patients with severe CKD who did not reach ESKD because of death or less progressive CKD. Fifth, the lack of outpatient predialysis nephrology care may reflect the patient’s preference not to receive nephrology care, the provider’s preference to not refer certain patients for such care, or the its substitution for inpatient nephrology care, which was not captured in our data. Finally, the use of surgical codes to identify vascular access may not indicate that the access is actually being used for dialysis and as such, may overestimate its use. While the USRDS Medical Evidence File contains data regarding vascular access at dialysis initiation, it only began including this information in 2005 and hence this source could not be used for our cohort.