Contribution of serum albumin to frailty-associated 1-year postoperative mortality among older patients: Mediation analysis of a prospective cohort

Frailty is a significant risk factor for postoperative mortality in elderly patients, but the underlying mechanisms remain poorly understood. Nutritional status, indicated by serum albumin, may play a mediating role in this relationship. In this prospective cohort study, 305 patients aged ≥65 years undergoing elective non-cardiac surgery were enrolled. Frailty was assessed using the Fried phenotype criteria. Serum albumin levels were measured perioperatively. The primary outcome was all-cause mortality within one year post-surgery. We employed multivariable regression models and causal mediation analysis to examine the relationship between frailty, albumin levels, and mortality, adjusting for relevant clinical covariates. The prevalence of frailty was 33.4% in the cohort. Frail patients demonstrated significantly higher mortality rates compared to non-frail patients (21% vs. 17%, p<0.05). Mediation analysis revealed that serum albumin mediated 22.66% of the total effect of frailty on 1-year mortality (indirect effect: 0.0416, 95% CI: 0.0087-0.083). Further analysis showed this mediation effect was particularly significant for the musculoskeletal components of frailty (weakness, slowness, and low physical activity). Serum albumin partially mediates the association between preoperative frailty and postoperative mortality in elderly surgical patients. These findings suggest that nutritional interventions targeting hypoalbuminemia may help reduce mortality risk in frail elderly surgical patients, though further interventional studies are needed to confirm this hypothesis.