Increased risks of severe CKD in elderly don’t always translate into increased mortality from kidney failure

Although the risk of developing severe chronic kidney disease (CKD) does increase dramatically with age, the risk of kidney failure in older patients who do develop CKD may not be as high as anticipated, according to results from a population-based study of approximately 4 million Canadians with CKD.

“This population-based cohort study found that the risk of death exceeded the risk of kidney failure in most people with stage IV CKD and that the risk of kidney failure decreased sharply with advancing age, regardless of comorbidity,” according to Pietro Ravani, MD, PhD, University of Calgary, Calgary, Alberta, Canada, and fellow researchers, who published their results in JAMA Network Open.

We reported for the first time, to our knowledge, how risks and probabilities change with advancing age overall and across categories defined by common comorbidities. We used population-based data, included people with newly identified stage IV CKD at high risk of both death and kidney failure, and used eligibility criteria that minimize the inclusion of people with acute kidney injury or prevalent patients (as opposed to incident patients),” they added.

Using data from the laboratory and administrative data set of Alberta Health, Ravani and colleagues identified 30,801 adults (mean age: 76.8 years; 56.1% female) living in Alberta with stage IV CKD — defined as an estimated glomerular filtration rate (eGFR) of 15-30 mg/min/1.73 m2 — whom they followed until the onset of kidney failure, death, or censoring.

In all, 17.9% of these patients developed kidney failure and 52.9% died. Researchers found that the incidence of stage IV CKD “increased sharply” with increasing age, while the absolute risk of kidney failure decreased. The risk of death also increased with increasing age, most markedly in patients aged 85 years or older.

Compared with the 5-year risk of death, the 5-year risk of kidney failure was higher in patients ˂65 years old, the same in those age 65 to 74 years, and lower in older patients.

In patients aged 75 years and older, the risk of death was significantly higher than risk of kidney failure, and this risk increased exponentially with age. From ages 75 to 84 years, it was 6-fold higher (0.51 [95% CI: 0.5-0.52] versus 0.09 [95% CI: 0.8-0.09], respectively). In patients aged 85 years or older, the risk was 25-fold higher (0.75 [95% CI: 0.74-0.76] vs 0.03 [95% CI: 0.02-0.03]). Between the ages of 85 to 94 years, the risk of death was 24-fold higher than the risk of kidney failure (0.73 [95% CI: 0.72-0.74] versus 0.03 [95% CI: 0.02-0.03], respectively), and after age 95 years, this risk was a full 149-fold higher (0.89 [95% CI: 0.87-0.92] versus ˂0.01 [95% CI: ˂0.01-0.01]).

These results have several implications for both clinical practice and future research, stressed Ravani and colleagues.

“First, the risk of death compared with the risk of kidney failure and the magnitude of each absolute risk are both important considerations when discussing prognosis with patients and their caregivers. Second, instead of offering education about treatment options for kidney failure to all people with eGFR below a particular threshold, such education may be more relevant for low-risk, younger people and for high-risk people regardless of age. Third, a graphical representation of how the individual absolute risks of death and kidney failure vary over time or at prespecified times that uses a decision aid may better help patients and caregivers understand their values and goals,” they concluded.

In an invited commentary, Ann M. O’Hare, MA, MD, of the VA Puget Sound Health Care System, Seattle, WA, noted an important difference in this population-based study.

“A novel feature of the study by Ravani et al compared with these earlier studies is that it defined kidney failure broadly to include individuals who reached the advanced stages of disease regardless of whether they were treated with dialysis,” she wrote.

O’Hare also agreed with these researchers regarding the value of these results for clinicians and patients alike.

“As Ravani et al point out, the presence of large systematic age differences in the association between eGFR and risks of kidney failure and death have important implications for care and treatment both at a population level and individual level. The greater likelihood that older adults with severely reduced eGFR will die with rather than from their kidney disease can inform policy and resource planning. This information can also help people with kidney disease to establish treatment goals and life priorities as their illness progresses.”

Limitations of the study include the inclusion of few African American patients, use of the Chronic Kidney Disease Epidemiology Collaboration’s equation to estimate kidney function that has not been well validated in older patients, and the lack of data necessary to determine any associations between pre-study eGFR decline and outcomes.

  1. Researchers of this population-based study found that although the incidence of severe CKD increases dramatically with older age, the risk of death is significantly higher than risks of kidney failure.

  2. In older patients with stage IV CKD age 75 to 84 years, death is 6 times more likely to occur than kidney failure, and in those aged 85 years and older it is 25 times more likely.

E.C. Meszaros, Contributing Writer, BreakingMED™

Ravani has received operating grants or foundation awards from the Canadian Institutes of Health Research, Alberta Innovates-Health Solutions, and the Canada Foundation for Innovation.

O’Hare has received grants from the National Institute of Diabetes and Digestive and Kidney Diseases, Centers for Disease Control and Prevention, and the Department of Veterans Affairs Health Services Research and Development Service; personal fees from the American Society of Nephrology, Nephrology, Kaiser Permanente Southern California, Hammersmith Hospital, Japanese Society of Dialysis and Transplant, Chugai Pharmaceutical Co Ltd, DEVENIR Foundation, Dialysis Clinic Inc, Fresenius Medical Care, and UpToDate; and personal fees and nonfinancial support from the Health and Aging Policy Fellowship Program outside the submitted work.

Cat ID: 127

Topic ID: 81,127,282,494,730,127,255,925