The association between cystatin C and frailty status in older men

Abstract

BACKGROUND Declining kidney function and frailty are common with aging, but the association between these conditions remains uncertain. We hypothesize that cystatin C predicts prevalent frailty status in men age 65 and older. METHODS Serum cystatin C (cys C) and creatinine (Cr) were measured and frailty status ascertained in a random sample of 1602 community-dwelling men age 􀂕 65 yrs participating in the MrOS study. Frailty status (comprised of shrinking, weakness, exhaustion, slowness and low physical activity) was analyzed as an ordinal outcome of robust, intermediate stage, and frail based on the number of frailty components present (0, 1-2, or 􀂕 3 respectively) using a multinomial logistic regression model to simultaneously evaluate the odds of being classified as intermediate vs. robust and frail vs. robust. The base model was adjusted for age, race, and clinical site. RESULTS The mean age of the cohort was 73.8 yrs; 9.8% were frail and 47.2% were intermediate stage. The highest quartile of cys C was associated with more than seven times the odds of being classified as frail vs. robust when compared to the lowest quartile of cystatin C and 2.38 times the odds of being classified as intermediate status. The association was attenuated but persisted after adjusting for health status, body mass index, number of comorbidities, IADL impairments, vitamin D level, serum albumin level, CRP and IL-6 levels. In contrast, neither higher serum Cr (p-value for trend across quartiles > 0.76) nor lower Cr-based eGFR (p-value for trend across quartiles > 0.47) was associated with higher odds of frailty. CONCLUSION Higher cys C was associated with increased odds of frailty status in this cohort of older men whereas Cr-based measures were not. This difference may be due to lower specificity of Cr based measures compared to cys C in older adults with modest reductions in kidney function, or because cys C is associated with frailty by a mechanism that is unrelated to kidney function.