Clinical Practices and Outcomes in Elderly Hemodialysis Patients: Results from the Dialysis Outcomes and Practice Patterns Study (DOPPS)

Discussion

Elderly patients account for an increasing fraction of patients on renal replacement therapy worldwide, reaching 25% to 30% in most ESRD registries (5,18). This phenomenon translates into higher health care costs and additional clinical challenges for health professionals to meet the often broader and more demanding health care needs of the geriatric population (19,20). To assess hemodialysis practices and outcomes among elderly versus younger patients in 12 countries, we evaluated recent data from the DOPPS, a large international hemodialysis population.

To our knowledge, this is the first study of size to describe hemodialysis practices among elderly patients from a broad international perspective and to report outcome data compared with younger counterparts treated in the same dialysis environments. The international nature of the DOPPS has allowed us to compare practices and outcomes across four geographic regions, representing the vast majority of the hemodialysis population worldwide. Our results are based upon cross-sections of patients representative of the typical in-center hemodialysis patient population seen on a given day in a dialysis unit.

The age distribution of patients enrolled in the DOPPS closely follows the current aging trend observed in the general population, with the mean age of DOPPS participants increasing significantly in most countries over the past decade. However, the proportion of elderly among in-center hemodialysis patients varied widely across countries, indicating possible differences in clinical practices and policies toward starting chronic hemodialysis in this population, and use of transplantation and peritoneal dialysis. The low proportion of elderly in Japan may be due in part to the low rates of kidney transplantation and peritoneal dialysis in Japan compared with other countries, coupled with Japan having one of the highest rates of ESRD incidence and longest hemodialysis patient survival. According to the Japanese Society for Dialysis Therapy Registry in 2005, 29.7% of patients starting dialysis and 21.5% of chronic dialysis patients were aged ≥75 years (21). In other countries having much higher transplantation rates, a substantial fraction of the younger healthier patients received a kidney transplant, thereby removing them from the pool of hemodialysis patients.

Comorbid conditions were common in elderly dialysis patients. Prevalence of coronary artery disease increased with age in all DOPPS countries, and was almost 3 times higher in patients aged ≥75 years versus those aged <45 years. Similarly, malignancies were 3 to 18 times more frequent in the elderly group. These findings are in agreement with epidemiologic studies showing that prevalence of cardiovascular events, and malignancies, increases almost linearly with aging (22,23). Interestingly, neurologic diseases and dementia were much higher among Japanese elderly participants. Because comorbidities are abstracted from the patient medical record, these differences may be in part explained by cultural differences in the diagnosis of these conditions.

Overall, hemodialysis prescription and clinical practices in elderly patients mainly reflected country-specific practices. Permanent central venous catheters were used more frequently in the elderly versus younger patients in Europe, ANZ, and North America but were very rarely used in Japan. Despite the differences in vascular access, mean prescribed blood flow rate was virtually identical in all age groups, between 295 and 395 ml/min, except for Japan, which displayed a mean blood flow rate between 184 and 207 ml/min. In all regions, the duration of dialysis session was about 15 minutes shorter among the elderly than in younger age groups. However, once the prescribed treatment time was normalized for body weight, no significant differences were observed across age groups. No differences were observed in delivered dialysis dose, as measured by single pool Kt/V. Maintenance of a satisfactory dialysis dose can be partially explained by the lower dry weight, lower lean body mass, and low serum albumin, which were common in the elderly group.

The mean ultrafiltration rate was lower in the elderly than in the younger age groups. This is likely explained by the lower dry weight as well as the high prevalence of cardiovascular disease and congestive heart failure observed among elderly patients, as reported in Table 1.

In Europe, ANZ, and North America, a higher percentage of elderly patients achieved the hemoglobin target value. This fact confirms that anemia correction is particularly a case-sensitive concern in the elderly dialysis population because benefits extend from enhancement of cardiac function and physical capacity to improvement of brain and cognitive functioning (24–26). Interestingly, in North America, Europe, and ANZ—but not in Japan—the erythropoietin resistance index was lower in elderly patients than in younger participants. Differences in clinical practices (e.g., targeted hemoglobin values) as well as in patient case-mix may contribute to differences in erythropoietin stimulating agent prescription observed across regions.

Malnutrition was consistently observed among elderly patients across the four regions as indicated by low serum albumin and low serum phosphorus. These findings suggest that two major mortality risk factors, low dietary protein intake and hypoalbuminemia, are common among elderly dialysis patients and require specific attention.

Quality of life for dialysis patients is reduced by almost 50% compared with that of the population worldwide (27). The deterioration of quality of life affects all dimensions, including the physical component, mental component, and burden of kidney disease with regional variations. Interestingly, among DOPPS elderly participants the physical component was significantly more affected than the mental component. These observations suggest that elderly patients are more restricted in their physical function than in their mental function. These results also correlate well with the observation that the fraction of patients who can walk without assistance substantially declined with older age in each study region (Table 1). It is however of interest that—in agreement with the general population—elderly dialysis patients were more likely to have high Center of Epidemiologic Studies Depression Rating Scale scores in Europe and in Japan, indicating the higher likelihood of possible clinical depression among elderly hemodialysis patients.

As expected, mortality rates were higher in elderly hemodialysis patients (28). Median survival for patients aged ≥75, 45 to 74, and <45 years was 3, 6, and 12 years, respectively. The relative risk of all-cause mortality increased linearly with each age group. It is important to note that acute factors (falls, fractures, orthopedic surgery, etc.), frequently observed in this frail population, may have contributed to increased mortality. However, advanced age is not the only predictive factor. Functional health status, comorbid conditions, caregivers' expertise, and social support also are determinant factors of survival (29,30). Interestingly, in Japan and North America diabetes was associated with a higher mortality risk in participants aged <75 but not in those ≥75 years. Elderly patients with diabetes may be overall healthier and therefore experience longer survival. Alternatively, late onset diabetes has a better prognosis in the elderly dialysis population than in the younger dialysis population. In addition, competing risks by other causes of death may substantially contribute to the observed relative ratio of death associated with diabetes among elderly hemodialysis patients. Cardiovascular disease was the most common cause of death among elderly patients but represented a lower percentage of events than in the younger age groups. Death due to discontinuation of dialysis was relatively common among elderly patients in North America (7.6%) and ANZ (14.3%) but not in Europe (3.5%) and Japan (0%), possibly reflecting cultural differences. It is worth noting that acute factors (e.g., stroke and surgery) may have precipitated the fatal event, leading nephrologists to voluntarily interrupt renal replacement therapy. There is ample debate in the international nephrology community surrounding the issues of denying or stopping hemodialysis treatment in elderly patients and use of alternative conservative therapeutic regimens (31–33).

The present study has some limitations that are mainly due to the observational nature of the DOPPS. The relationships that we have described between patient age groups, practices, and mortality are factual and not causal. The cross-sectional DOPPS sample may be biased by the fact that healthier patients will survive longer on dialysis. Despite adjustment for a wide variety of patient clinical characteristics, we cannot exclude that this may also affect our findings. Moreover, economic considerations and consequences concerning renal replacement therapy in elderly patients have not been evaluated. Although elderly patients have access to dialysis treatment in all DOPPS countries, it is possible that some restrictions in starting dialysis are applied for elderly patients with chronic kidney disease stage 5. Unfortunately, the DOPPS is not able to address this specific issue. Finally, the DOPPS includes only in-center hemodialysis patients; therefore, our findings are not applicable to ESRD patients receiving other modalities of renal replacement therapy.

On the basis of international DOPPS data, hemodialysis prescription in elderly patients was overall similar to that in younger age groups and tended to follow region-specific practices. Deterioration of quality of life affected the physical but not the mental component scores. Mortality risk was markedly higher in the elderly group but this was likely related to comorbid conditions and possibly to functionality at baseline.

Elderly dialysis patients represent a selected group of patients who can be considered survivors and are not representative of the general nonrenal population. Interventional studies on elderly dialysis patients comparing renal replacement therapy modalities (peritoneal dialysis, home hemodialysis, and hemodiafiltration) or introducing specific prescriptions such as longer treatment time, nutritional support, and a personalized treatment schedule should be evaluated (31). Social support for elderly patients must be considered as a determinant factor that affects dialysis outcomes. Further interventional studies in elderly dialysis patients deserve to be evaluated in the future to optimize the renal care and practice of this population.