Abstract: Objective To examine the association between frailty transitions and distinct multimorbidity patterns in relation to mortality risk among hospitalized older adults. Methods This prospective cohort study enrolled 8 270 hospitalized elderly patients aged 65 years and above. Frailty status was assessed using the FRAIL scale,and patients were classified into five categories based on frailty trajectories at baseline and 3-month follow-up. Principal component analysis was used to identify five distinct multimorbidity patterns,and their impact on mortality risk was evaluated. Results A total of 56.77% of participants exhibited multimorbidity,and frailty trajectories were closely associated with mortality risk. The mortality risk for patients in the persistent frailty and worsening frailty groups was 14.27 times and 10.02 times higher,respectively, compared to the persistent non-frail group. Multimorbidity patterns,such as cardiometabolic disorders,sensory-psychiatric impairments,and cancer,significantly increased mortality risk. Conclusions Frailty trajectories and multimorbidity patterns significantly influence the mortality risk in hospitalized elderly patients. Early identification and intervention for the risk factors of frailty and multimorbidity are crucial for slowing disease progression and improving the health of the elderly population.

Key words: frailty, comprehensive comorbidity index, multimorbidity model, mortality, mohort study