Changes in survival among elderly patients initiating dialysis from 1990 to 1999

Abstract

Background: Over the past decade, there has been a steep rise in the number of people with complex medical problems who require dialysis. We sought to determine the life expectancy of elderly patients after starting dialysis and to identify changes in survival rates over time.

Methods: All patients aged 65 years or older who began dialysis in Canada between 1990 and 1999 were identified from the Canadian Organ Replacement Register. We used Cox proportional hazards models to examine the effect that the period during which dialysis was initiated (era 1, 1990-1994; era 2, 1995-1999) had on patient survival, after adjusting for diabetes, sex and comorbidity. Patients were followed from initiation of dialysis until death, transplantation, loss to follow-up or study end (Dec. 31, 2004).

Results: A total of 14,512 patients aged 65 years or older started dialysis between 1990 and 1999. The proportion of these patients who were 75 years or older at the start of dialysis increased from 32.7% in era 1 (1990-1994) to 40.0% in era 2 (1995-1999). Despite increased comorbidity over the 2 study periods, the unadjusted 1-, 3- and 5-year survival rates among patients aged 65-74 years at dialysis initiation rose from 74.4%, 44.9% and 25.8% in era 1 to 78.1%, 51.5% and 33.5% in era 2. The respective survival rates among those aged 75 or more at dialysis initiation increased from 67.2%, 32.3% and 14.2% in era 1 to 69.0%, 36.7% and 20.3% in era 2. This survival advantage persisted after adjustment for diabetes, sex and comorbidity in both age groups (65-74 years: hazard ratio [HR] 0.76, 95% confidence interval [CI] 0.72- 0.81; 75 years or more: HR 0.86, 95% CI 0.80-0.92).

Interpretation: Survival after dialysis initiation among elderly patients has improved from 1990 to 1999, despite an increasing burden of comorbidity. Physicians may find these data useful when discussing prognosis with elderly patients who are initiating dialysis.

Figure 1: Survival curves for patients aged 65–74 years and those aged 75 or more who began dialysis during 1990–1994 (era 1, solid lines) and 1995–1999 (era 2, dotted lines). Curves have been adjusted for sex; presence or absence of baseline cerebrovascular disease or peripheral vascular disease; previous myocardial infarction or coronary artery bypass surgery; diabetes at time of starting dialysis; neoplasia at time of starting dialysis; and initial dialysis modality.

Figure 2: Adjusted risk of death following initiation of dialysis among patients aged 65–74 years at the time of starting dialysis (based on 9076 of 9096 patients who had complete data). Point estimates show the estimated hazard ratio associated with each variable; the 95% confidence interval (CI) around the estimate is shown as a horizontal bar. The variable “era effect” is the hazard ratio for death between patients who began dialysis in era 2 (1995–1999) and those who began it in era 1 (1990–1994). Vascular disease is defined as the presence of either peripheral vascular disease or cerebrovascular disease, or both, at the time of dialysis initiation.

Figure 3: Adjusted risk of death following initiation of dialysis among patients aged 75 years or more at the time of starting dialysis (based on 5390 of 5411 patients who had complete data). Point estimates show the estimated hazard ratio associated with each variable; the 95% confidence interval (CI) around the estimate is shown as a horizontal bar. The variable “era effect” is the hazard ratio for death between patients who began dialysis in era 2 (1995–1999) and those who began it in era 1 (1990–1994). Vascular disease is defined as the presence of either peripheral vascular disease or cerebrovascular disease, or both, at the time of dialysis initiation.