Age Interacts with Kidney Measures on Mortality Risk

Although effects on relative versus absolute risk differ, low estimated glomerular filtration rate (eGFR) and high albuminuria are linked to increased mortality in all age groups, reports a study in The Journal of the American Medical Association.

The meta-analysis examined whether age modified the associations of eGFR and albuminuria with clinical outcomes. The investigators pooled individual-level data on more than 2 million members of Chronic Kidney Disease Prognosis Consortium (CKD-PC) cohorts. The data included 33 non-kidney disease cohorts (general population or people at high vascular disease risk) and 13 CKD cohorts. Clinical associations with eGFR and albuminuria were examined across age groups, with adjustment for other risks.

In non-CKD cohorts, individuals with lower eGFR and higher albuminuria were at higher risk of death and end stage renal disease (ESRD). At an eGFR of 45 mL/min/1.73 m2 (versus 80 mL/min/1.73 m2), the adjusted hazard ratio for death decreased with age: from 3.50 for people aged 18 to 54 years, to 2.21 at 55 to 64 years, 1.59 for 65 to 74 years, and 1.35 at 75 years or older. In contrast, absolute risk increased with age: excess deaths per 1000 person-years were 9.0, 12.2, 13.3, and 27.2, respectively.

The absolute risk of death associated with higher levels of albuminuria also increased with age. At an albumin-creatinine ratio of 300 mg/g (versus 10 mg/g), excess mortality per 1000 person years was 7.5 at 18 to 54 years, 12.2 per 1000 at 55 to 64 years, 22.7 per 1000 at 65 to 74 years, and 34.3 per 1000 at age 75 or older.

The CKD cohorts showed no age-related decrease in the adjusted relative hazards of mortality. For all cohorts, the relative risks of ESRD and the absolute risk differences associated with both kidney markers were similar across age groups.

It has been suggested that the CKD classification system should be revised to include a combination of eGFR and albuminuria levels. Before this is done, it is important to understand how age affects the clinical risks associated with these measures.

This meta-analysis finds that low eGFR and high albuminuria affect mortality risk in all age groups, across a wide range of populations. At older ages, the relative risk is lower but the absolute risk differences are higher. The researchers call for “a common definition and staging of CKD based on eGFR and albuminuria for all age groups” [Hallan SI, et al: Age and association of kidney measures with mortality and end-stage renal disease. JAMA. 2012; doi:10.1001/jama.2012.16817].

December 2012 (Vol. 4, Number 12)