Kidney Failure Untreated More Often in Older Adults

The progression rate of untreated kidney failure is significantly higher in older compared with younger individuals, according to a study of almost 2 million Canadian adults. [JAMA. 2012;307(23):2507-2512].

In a study to determine whether age is associated with the likelihood of treated kidney failure, researchers conducted a retrospective cohort study using laboratory and administrative data from Alberta, Canada to identify 1,816,824 adults who had outpatient estimated glomerular filtration rate (eGFR) measured with a baseline eGFR of 15 mL/min/1.73 m² or higher. The eGFRs were measured between May 1, 2002, and March 31, 2008, and none of the patients required renal replacement therapy at study onset.

The investigators performed analyses stratifying age as 18 to 44, 45 to 54, 55 to 64, 65 to 74, 75 to 84, and ≥85 years and eGFR as ≥90, 60 to 89, 45 to 59, 30 to 44, and
15 to 29 mL/min/1.73m². The primary outcome measures were adjusted rates of treated kidney failure, untreated kidney failure (progression to eGFR <15 mL/min/1.73m² without renal replacement therapy), and mortality.

The findings showed that 97,451 patients (5.36%) died, 3295 (0.18%) developed kidney failure that was then treated, and 3116 (0.17%) developed untreated kidney failure during the median follow-up of 4.4 years. Furthermore, within each eGFR stratum, adjusted rates of death increased with increasing age. For example, in the eGFR stratum of 15 to 29 mL/min/1.73m², the mortality rates were nearly 11-fold higher for participants ≥85 years of age, compared with those 18 to 44 years of age (adjusted rate, 131.93; 95% confidence interval [CI], 116.62-149.27 vs 12.07; 95% CI, 4.69-31.06, per 1000 person-years, respectively; P<.001).

In the eGFR stratum of 15 to 29 mL/min/1.73m², adjusted rates of treated kidney failure per 1000 person-years were more than 10-fold higher among the youngest (18-44 years of age), compared with the oldest (≥85 years of age) group (adjusted rate, 24.00; 95% CI, 14.78-38.97 vs 1.53; 95% CI, 0.59-3.99, per 1000 person-years, respectively; P<.001).

However, opposite results were found for adjusted rates of untreated kidney failure with more than a 5-fold increase among the oldest (≥85 years of age), compared with the youngest (18-44 years of age) participants (adjusted rate, 19.95; 95% CI, 15.79-25.19 vs 3.53; 95% CI, 1.56-8.01, per 1000 person-years, respectively; P<.001). Overall, rates of kidney failure (treated and untreated combined) showed less variation across age groups. For example, the adjusted rate of those with an eGFR of 15 to 29 mL/min/1.73m² was 36.45 (95% CI, 24.46-54.32) among individuals 18 to 44 years of age and 20.19 (95% CI, 15.27-26.69) among participants ≥85 years of age (P=.01).

The researchers cited study limitations. The investigators were unable to assess the reasons some patients in the cohort did not initiate dialysis despite low eGFR. The cohort was limited to adults who had at least 1 serum creatinine measurement as part of their medical care and, as such, may have included more adults with underlying comorbidity. Long-term prognosis for patients with treated and untreated renal failure was not available due to insufficient follow-up. Finally, it is possible that outcomes would have differed if kidney function were classified using values obtained by a population-based survey.

“These findings have important implications for clinical practice and decision making; coupled with the finding that many older adults with advanced CKD [chronic kidney disease] are not adequately prepared for dialysis, these results suggest a need to prioritize the assessment and recognition of CKD progression among older adults,” concluded the researchers.