The mediating pathways of frailty on healthcare costs and length of stay in older patients with colorectal cancer: a multicenter retrospective study

Abstract

Background The relationship between frailty and healthcare resource utilization in older patients with colorectal cancer (CRC) remains insufficiently quantified. We evaluated the associations of frailty with high inpatient costs, length of stay (LOS), and adverse events, and examined the explanatory roles of co-occurring comorbidity burden and postoperative complications. Methods This multicenter retrospective study analyzed 4,936 patients aged ≥60 years undergoing elective CRC surgery between 2014 and 2024. Hierarchical multivariable regression models evaluated associations between frailty and outcomes. Mediation-style decomposition was used to estimate the extent to which comorbidity burden and postoperative complications explained frailty-associated differences in high inpatient costs and LOS. A simulation-based sensitivity analysis was performed to assess the potential impact of ICD-10-based frailty misclassification. A Bonferroni-corrected threshold of p < 0.006 was applied. Results Frailty was significantly associated with high inpatient costs (OR = 1.274, 95% CI: 1.083–1.498, p = 0.003), prolonged LOS (log-transformed β = 0.082, 95% CI: 0.053–0.111, p < 0.001), and adverse events (OR = 3.317, 95% CI: 2.267–4.854, p < 0.001). Mediation-style decomposition showed that co-occurring comorbidity burden explained 28.6% of frailty-associated difference in high inpatient costs (p < 0.001). Postoperative complications did not significantly explain the frailty–LOS association (3.8%, p = 0.368). The estimated excess socioeconomic burden associated with frailty was CNY 657 million. In the sensitivity analysis, the direction of frailty associations with all three outcomes remained unchanged across simulated ICD-10 misclassification scenarios, although the association with high inpatient costs was attenuated under moderate and severe assumptions. Conclusion Frailty was associated with increased healthcare resource utilization and adverse outcomes in older CRC patients. Co-occurring comorbidity burden partly explained the frailty-associated difference in high inpatient costs, whereas prolonged LOS was not significantly explained by postoperative complications. These findings support routine frailty screening and dual-track perioperative optimization targeting both comorbidity burden and frailty-related physiological vulnerability.