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Study finds significantly higher rate of untreated kidney failure among older adults

June 27, 2012– In a study that included nearly 2 millions adults in Canada, the rate of progression to untreated kidney failure was considerably higher among older adults, compared to younger individuals, according to a study in the June 20 issue of JAMA.

"Studies of the association among age, kidney function, and clinical outcomes have reported that elderly patients are less likely to develop end-stage renal disease (ESRD) compared with younger patients and are more likely to die than to progress to kidney failure even at the lowest levels of estimated glomerular filtration rate [eGFR; flow rate of filtered fluid through a kidney]," according to background information in the article. Previous studies have defined kidney failure by receipt of long-term dialysis, which reflects both disease progression and a treatment decision.

 "Because it is plausible that the likelihood of initiating long-term dialysis among individuals with kidney failure varies by age, earlier studies may provide an incomplete picture of the burden of advanced kidney disease in older adults, based on the incidence of long-term dialysis alone."

Brenda R. Hemmelgarn, M.D., Ph.D., of the University of Calgary, Alberta, Canada, and colleagues conducted a study to determine whether age is associated with the likelihood of treated kidney failure (renal replacement therapy: receipt of long-term dialysis or kidney transplantation), untreated kidney failure, and all-cause mortality.

The study included 1,816,824 adults in Alberta, Canada, who had outpatient eGFR measured between May 2002 and March 2008, with a baseline eGFR of 15 mL/min/1.73 m2 or higher and who did not require renal replacement therapy at the beginning of the study.

The primary outcome measures for the study were adjusted rates of treated kidney failure, untreated kidney failure (progression to eGFR <15 mL/min/1.73 m2 without renal replacement therapy), and death.

During a median (midpoint) follow-up of 4.4 years, 97,451 (5.4 percent) of study participants died, 3,295 (0.18 percent) developed treated kidney failure, and 3,116 (0.17 percent) developed untreated kidney failure. The researchers found that within each eGFR stratum, adjusted rates of death increased with increasing age.

Also, within each eGFR stratum, rates of treated kidney failure were consistently higher among the youngest age group. "For example, in the lowest eGFR stratum (15-29 mL/min/1.73 m2), adjusted rates of treated kidney failure were more than 10-fold higher among the youngest (18-44 years) compared with the oldest (85 years or older) groups," the authors write.

The opposite results were evident for untreated kidney failure. The risk of untreated kidney failure increased with lower vs. higher eGFR categories, and this association was stronger with increasing age. "For the lowest eGFR stratum (15-29 mL/min/1.73 m2), adjusted rates of untreated kidney failure were more than 5-fold higher among the oldest age stratum (85 years or older) compared with the youngest age stratum (18-44 years)."

Rates of kidney failure overall (treated and untreated combined) demonstrated less variation across age groups.

The researchers write that their results suggest that the incidence of advanced kidney disease in the elderly may be substantially underestimated by rates of treated kidney failure alone.

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

"Our findings also imply that clinicians should offer dialysis to older adults who are likely to benefit from it—and should offer a positive alternative to dialysis in the form of conservative management (including end-of-life care when appropriate) for patients who are unlikely to benefit from (or prefer not to receive) long-term dialysis.

"Given the large number of older adults with severe CKD, these results also highlight the need for more proactive identification of older adults with CKD, assessment of their symptom burden, and development of appropriate management strategies. Finally, our study demonstrates the need to better understand the clinical significance of untreated kidney failure, the factors that influence dialysis initiation decisions in older adults, and the importance of a shared decision making process for older adults with advanced CKD."