When an elderly person, especially the very old (≥85 years old), faces the possibility of dialysis, the nephrologist often has difficulties making treatment decisions as he or she must consider many aspects regarding the patient's underlying condition and probable outcome 
. These decisions must also be faced by both the patients and their families, as they share in the decision making. Mortality in elderly patients has been closely correlated with many comorbidities independent of age 
. Therefore, some scoring systems have been developed to help the physician assess whether a dialysis patient will live long enough to benefit from the therapy and have their life span prolonged 
. However, most studies have not focused on elderly dialysis patients, some of whom may need several clinical assessments and laboratory datasets just to predict short-term (6–12 months) survival 
. For all of these scoring systems, age has always been a strong independent predictive factor. Liu et al. modified the CCI without including the age factor and developed the nCI to analyze outcomes for dialysis patients 
. The nCI was found to have a good predictive value and was reliably reproducible in the large USRDS database dialysis population. Our study used the nCI and Taiwan's NHIRD dialysis population to try to develop a relatively easy approach to predict the outcomes of elderly patients after beginning dialysis. We found that the patients in the highest score group had the highest mortality risk, and that after 5 years of dialysis, the survival rate of patients in the lowest score group was three times better than that of patients in the highest score group. In addition, this study compared the nCI with the Charlson comorbidity index using the predictive ability statistic (c-statistic for time-to-event data). The c-statistics used to measure to what extent predicted values from the model. This study found the c-statistics value of nCI score to be 0.90782 (95% CI: 0.89685–0.91823), while that of Charlson comorbidity index (CCI) score to be 0.90035 (95% CI: 0.88901–0.91115). Therefore, the two models were found to have virtually identical performance. However, when applying the nCI, a physician would not need to consider as many comorbid condition variables as CCI, which would make it simpler and more convenient to use in clinical practice.
Age was not included in the comorbidity index of the nCI because it is difficult to “sum” the effects of age and comorbid conditions while assigning definite scores 
. However, we stratified the four score groups by age and found a good correlation between age group and survival rate. During 1999–2000 period, the estimated life expectancy of the general population in Taiwan was 76.5 years (male: 73.8 years; female: 79.6 years) 
, and most elderly patients (especially those ≥70 years) with lower nCI scores lived almost that long. In addition, the number of comorbid conditions may also reveal an inverse relationship with the quality of life 
. Therefore, we can expect that elderly dialysis patients with lower nCI scores to live with a quality of life almost as good as that of the elderly in the general population. One Canadian study found the mean life expectancy of 75- to 80-year-old dialysis patients to be 3.2 years 
. This is only slightly longer life than the expectancy in our study population, especially for patients with lower nCI scores.
In contrast, our study found patients with higher nCI scores to have a shorter life expectancy. Similarly, one recent study found that dialysis may not be beneficial for the survival of patients over 75 years old who have multiple comorbidities and cardiac ischemia 
. Although dialysis definitely provides a life-sustaining therapy and extends patients' lives, it may also aggravate or prolong a patient's suffering for the remainder of his or her life, and even extend the dying process. Elderly dialysis patients may suffer from a substantial and sustained deterioration of functional status after beginning dialysis, especially if they reside in nursing home 
. Because elderly patients generally have more comorbid conditions than younger patients, they may suffer more in daily life from the related complications. For example, PVD-related amputation causes not only severe functional impairment, but also presents a huge health burden in many countries 
. In such a population, we might consider renal palliative care over dialysis for elderly patients >75 years old who have more comorbidities (i.e., higher nCI scores), especially those with poor daily living status 
According to the Renal Physicians Association and the American Society of Nephrology (RPA/ASN) guidelines 
, pre-ESRD patients and their families should receive clear information about their prognosis and all treatment options before shared decision making about whether or not to begin dialysis. However, these guidelines do not provide specific reliable means for making an overall prognosis estimate in octogenarians 
. Several studies also found that patients with poor outcomes still expected their physicians to explain their prognosis in detail 
. Our study provided quantitative estimates of life expectancy in different nCI score groups and age groups. These findings may support the physician for satisfactory explanations to elderly patients about to begin dialysis and also be used to encourage patients without many comorbid conditions (low nCI scores).
This study found elderly women comprise over half of this dialysis population in Taiwan. This preponderance of women in Taiwan dialysis population has been also found in another published study using NHIRD 
. This study also found 51.5% of the patients to belong to the lowest nCI score group. One possible explanation for this preponderance is that elderly patients with chronic kidney disease may have high rates of multiple comorbid conditions 
and, therefore, may die at a younger age because of the related complications of their underlying chronic diseases (such as DM, CAD, and CHF). They would be expected to have a relatively shorter life span without facing the choice of dialysis. In addition, there is the possibility of selection bias, since elderly patients with ESRD and multiple comorbid conditions might be more likely to be treated with palliative therapy because of their short life expectancy and would, thus, not live as long as those undergoing dialysis 
. Nevertheless, we found significant differences in survival between the four nCI score groups. Because many of these elderly patients were in the lowest nCI score group with relatively few comorbid extrarenal conditions at the beginning of dialysis, age alone should not be the only or the most important consideration for decision-making. More aggressive dialysis therapy should be considered a preferred choice for patients in the low nCI score group, even for octogenarians 
This study has several important limitations. First, there is no definite classification of severity for each comorbid condition and functional status. However, according to the NHI payment provisions, all treatment procedures and medications require an associated diagnostic code. Therefore, while we recorded the diagnostic codes given to each patient, comorbid disease severity should be “clinically evident” based upon the prescribed treatment. Even if we underestimated the prevalence of comorbidities, the nCI system provided a good predictive value. Second, using this billing database, we were unable to consider body mass index, actual blood pressure, specific data on dialysis adequacy, type of vascular access used for HD patients, laboratory data, and medical prescriptions, which may also have affected each patient's survival. We were also unable to identify functional status, an important prognostic factor in elderly dialysis patients. Third, although the nCI seemed to have the identical performance as CCI, we did not to validate the nCI with the categories in an independent population. Finally, it would be better to describe the causes of death for further analyses. Unfortunately, the Taiwan Bureau of National Health Insurance does not make available the cross-link information between it NHI database and “causes of death” database.