Transitions in Frailty and 4-Year Mortality Risk in Taiwan Longitudinal Study on Aging

Objectives: To explore the associations of (1) the frailty phenotype or frailty index transition with cause-specific mortality, and (2) different combinations of transition in frailty phenotype and frailty index with all-cause mortality. Design: Retrospective cohort study. Setting and Participants: Data from 3529 respondents aged >50 years who completed the 1999 and 2003 surveys of the Taiwan Longitudinal Study on Aging were analyzed. Methods: Cox regression and subdistribution hazard models were constructed to investigate frailty phenotype or frailty index transitions (by categories of frailty phenotype, absolute and percentage changes in frailty index, and combined categories of the 2 measurements) and subsequent 4-year all-cause and cause-specific mortality, respectively. Results: Among the frailty phenotype transition groups, the improved frailty group had overall mortality risk comparable to that of the maintained robustness/prefrailty group [hazard ratio (HR): 0.9; 95% CI: 0.7–1.2] and lower risk of mortality due to organ failure (HR: 0.4; 95% CI: 0.2–0.8; P = .015), whereas the worsened frailty group had the highest risk of all-cause mortality and death from infection, malignancy, cardiometabolic/cerebrovascular diseases, and other causes (HR: 1.8–3.7; all P < .03). The rapidly increased frailty index group had significantly higher all-cause and every cause-specific mortality than the decreased frailty index group (HR: 1.8–7.7; all P < .05). When frailty phenotype and frailty index transition groups were combined, participants with worsened frailty/rapidly increased frailty index had increased risk under the same frailty index/frailty phenotype transition condition, particularly for large changes in each factor (HR: 1.5–2.2; P < .01 for worsened frailty; 1.7–4.5, P < .03 for rapidly increased frailty index). Conclusions and Implications: We found that considering both frailty phenotype and frailty index provided best mortality prediction. These associations were independent of baseline frailty status and comorbidities. Nevertheless, even capturing transitions in frailty phenotype or frailty index only can provide good mortality prediction, which supported adopting these approaches in different clinical settings.