Association of Serum Creatinine‐Cystatin C Ratio With Hospital‐Associated Complications and Post‐Discharge Mortality

Aim To examine the associations of serum creatinine‐cystatin C ratio (CCR) at admission with mortality at 3 months post‐discharge and the incidence of hospital‐associated complications (HAC). Methods The study was conducted at 2 centers and included patients admitted to and discharged from geriatric wards between October 2019 and July 2023. Patient backgrounds were compared according to mortality at 3 months post‐discharge. Next, logistic regression analysis was performed using mortality at 3 months post‐discharge as the objective variable. Similarly, logistic regression analysis was performed with the incidence of HAC as the objective variable. Results Two hundred thirty‐one patients were included in the analysis. The death group had significantly lower CCR ( p < 0.001). In logistic regression analysis adjusted for age and sex, a low CCR was associated with increased mortality (odds ratio 3.260, p = 0.003). This association remained significant even after additional adjustment for kidney function (odds ratio 2.710, p = 0.014). The lowest CCR quartile showed a similar trend with an increased risk of death at 3 months compared to the highest quartile, even after extensive adjustment for demographics, kidney function, comorbidities, frailty, and cognitive function (Odds Ratio 4.157, p = 0.086). On the other hand, no significant association was found between CCR and the incidence of HAC. Conclusions A low CCR predicted higher post‐discharge mortality after basic adjustment; although the association attenuated when frailty and cognition were included, a risk increase persisted for the lowest versus highest quartile. Measuring CCR in hospitalized older adults may be useful for early identification of patients at high risk of death.