Association between eGFR and Disability-Free Survival in Older Adults Varies by Physical Function

BACKGROUND: Ascertaining the clinical relevance of reduced eGFR in older adults is challenging, particularly in those who may have decreased creatinine due to low muscle mass. This study investigated the potential of gait speed and grip strength (markers of muscle mass) to support the clinical interpretation of eGFR and its association with disability-free survival in older adults. METHODS: This was a cohort study of the ASPirin in Reducing Events in the Elderly (ASPREE) randomized trial and the ASPREE-eXtension observational follow-up study. Participants were recruited from community-based clinics. ASPREE enrolled adults aged ≥70 years, with African American and Hispanic adults eligible from age ≥65 years, all of whom were free of significant co-morbidity at baseline. Baseline eGFR categories (<60, 60-79, ≥80mL/min/1.73m2) combined with gait speed (<or ≥1 m/s), and in separate models, baseline eGFR categories combined with grip strength (weak vs not weak), were used as explanatory variables. Outcomes were disability-free survival, all-cause mortality, independence-limiting physical disability, or dementia. Survival analyses with undertaken with reference to individuals with 'eGFR 60-79mL/min/1.73m2 and slow gait' or 'eGFR 60-79mL/min/1.73m2 and not weak'. RESULTS: There were 16,925 participants, median follow-up was 8.4 years (interquartile range [IQR]:2.7,9.6), mean age was 75.0±4.5 years, and median eGFR was 79mL/min (IQR:68,89). In the presence of normal gait speed or grip strength, eGFR <60mL/min/1.73m2 did not increase the risk for disability-free survival or its components. Slow gait or weak grip accompanying any eGFR was associated with reduced disability-free survival, increased mortality, or increased disability. E.g: participants with eGFR ≥80mL/min/1.73m2 and slow gait were at risk for dementia (HR:1.48, 95%CI:1.23-1.79). CONCLUSIONS: In older, initially healthy adults, assessment of gait speed and grip strength may provide additional context when examining associations between eGFR and disability-free survival and its individual components.