Cystatin C and creatinine-based eGFR levels and their correlation to long-term morbidity and mortality in older...

The prevailing diagnostic criteria for CKD are age-independent, but have been challenged in light of the eGFR decline associated with normal aging. The stages of CKD communicate magnitude of risk of ESRD, cardiovascular morbidity, and mortality.

This study aims to provide more insight into the morbidity and mortality associated with eGFR levels corresponding to the current CKD stages in older adults.

The 2931 older adults in the Good Aging in Skåne study were randomized from the general population. The exposure variable used was eGFR level (CKD-EPI based on creatinine and cystatin C) with eGFR 60-89 mL/min/1.73 m² as a reference; the outcomes were mortality, acute cardiovascular disease, congestive heart failure, and rapid kidney function decline (RKFD; defined as a decline in eGFR by 3 mL/min/1.73 m² per year or more).

The mean age at baseline was 73 (SD 11) and mean follow-up time 11 (SD 5) years. Mortality was higher at lower eGFR levels with adjusted HR (95% CI) being 1.58 (1.34-1.88), 1.22 (1.05-1.41), 1 (reference), and 0.90 (0.67-1.21) for eGFR < 45, 45-59, 60-89 and ≥ 90 mL/min/1.73 m², respectively. For acute CVD the adjusted HR (95% CI) were 1.23 (0.81-1.87), 1.21 (0.87-1.69), 1 (reference), and 0.53 (0.28-1.00) for the same eGFR levels.

This study confirms that mortality in older adults increases with decreasing eGFR at eGFR levels below today's threshold for CKD. The correlation was less certain for lower eGFR and incident cardiovascular disease.