Association Between Pre-existing Comorbidities and Post-admission Complications and Outcomes in Older Trauma Patients Using a Nationwide Trauma Registry Database in Japan

Objective This study aims to identify preexisting comorbidities associated with increased in-hospital mortality among older trauma patients and to examine whether specific comorbidities are linked to distinct clinical outcomes characterized by severe post-admission complications. Methods This study included 77,336 patients aged ≥65 years with blunt or penetrating trauma who were admitted to participating facilities of the Japan Trauma Data Bank between January 2019 and December 2023. Patients with out-of-hospital cardiac arrest (OHCA) were excluded. Cox proportional hazards regression was performed using age, sex, trauma type (blunt or penetrating), presence or absence of severe injury in nine Abbreviated Injury Scale (AIS) regions, trauma severity scores (Revised Trauma Score and Injury Severity Score), and individual components of the Charlson Comorbidity Index (CCI) as explanatory variables. Survival time was defined as the dependent variable, and in-hospital outcome was treated as the event. Among CCI items significantly associated with mortality, hierarchical cluster analysis using Ward’s method was conducted to identify the patterns of preexisting comorbidities. Furthermore, Fisher's exact test was used to evaluate associations between individual CCI items and postoperative in-hospital complications related to mortality, including central nervous system, cardiovascular, gastrointestinal, and urinary tract complications; acute renal failure; abdominal compartment syndrome; pneumonia; disseminated intravascular coagulation (DIC); sepsis; and infections. Results In the Cox proportional hazards analysis, the CCI components with the highest hazard ratios (HR) for hospital mortality were metastatic solid tumors (HR: 2.926), moderate or severe liver disease (HR: 2.860), moderate or severe renal impairment (HR: 1.888), leukemia (HR: 1.782), congestive heart failure (HR: 1.667), mild liver disease (HR: 1.474), connective tissue disease (HR: 1.417), and chronic lung disease (HR: 1.365) (all p<0.05). Most comorbidities show broad, non-specific associations across multiple complication categories, while connective tissue disease showed a comparatively narrower pattern confined to central nervous system and urinary system complications. Moreover, hierarchical cluster analysis showed that connective tissue disease formed the most distinct cluster among the eight mortality-associated CCI components. Conclusion In-hospital mortality among older trauma patients was associated not only with trauma severity but also with eight preexisting comorbidities included in the CCI. Pre-existing cardiac, pulmonary, hepatic, or renal dysfunction, as well as malignancy, were independent risk factors for mortality following blunt or penetrating trauma. Among these comorbidities, connective tissue disease was associated with a unique pattern of complications following hospitalization, suggesting a different occurrence of complications compared with other preexisting conditions in older trauma patients.