Accounting for Age in the Definition of Chronic Kidney Disease

Using the same level of estimated glomerular filtration rate (eGFR) to define chronic kidney disease (CKD) regardless of patient age may classify many elderly people with a normal physiological age-related eGFR decline as having a disease.

To compare the outcomes associated with CKD as defined by a fixed vs an age-adapted eGFR threshold.

This population-based cohort study was conducted in Alberta, Canada and used linked administrative and laboratory data from adults with incident CKD from April 1, 2009, to March 31, 2017, defined by a sustained reduction in eGFR for longer than 3 months below a fixed or an age-adapted eGFR threshold. Non-CKD controls were defined as being 65 years or older with a sustained eGFR of 60 to 89 mL/min/1.73 m2 for longer than 3 months and normal/mild albuminuria. The follow-up ended on March 31, 2019. The data were analyzed from February to April 2020.

A fixed eGFR threshold of 60 vs thresholds of 75, 60, and 45 mL/min/1.73 m2 for age younger than 40, 40 to 64, and 65 years or older, respectively.

Competing risks of kidney failure (kidney replacement initiation or sustained eGFR <15 mL/min/1.73 m2 for >3 months) and death without kidney failure.

The fixed and age-adapted CKD cohorts included 127 132 (69 546 women [54.7%], 57 586 men [45.3%]) and 81 209 adults (44 582 women [54.9%], 36 627 men [45.1%]), respectively (537 vs 343 new cases per 100 000 person-years). The fixed-threshold cohort had lower risks of kidney failure (1.7% vs 3.0% at 5 years) and death (21.9% vs 25.4%) than the age-adapted cohort. A total of 53 906 adults were included in both cohorts. Of the individuals included in the fixed-threshold cohort only (n = 72 703), 54 342 (75%) were 65 years or older and had baseline eGFR of 45 to 59 mL/min/1.73 m2 with normal/mild albuminuria. The 5-year risks of kidney failure and death among these elderly people were similar to those of non-CKD controls, with a risk of kidney failure of 0.12% or less in both groups across all age categories and a risk of death at 69, 122, 279, and 935 times higher than the risk of kidney failure for 65 to 69, 70 to 74, 75 to 79, and 80 years or older, respectively.

This cohort study of adults with CKD suggests that the current criteria for CKD that use the same eGFR threshold for all ages may result in overestimation of the CKD burden in an aging population, overdiagnosis, and unnecessary interventions in many elderly people who have age-related loss of eGFR.