Transitions in frailty status in older adults in relation to mobility: A multistate modeling approach employing a deficit count

OBJECTIVES: To investigate how changes in frailty status and mortality risk relate to baseline frailty state, mobility performance, age, and sex. DESIGN: Cohort study. SETTING: The Yale Precipitating Events Project, New Haven, Connecticut. PARTICIPANTS: Seven hundred fifty-four communitydwelling people aged 70 and older at baseline followed up at 18, 36, and 54 months. MEASUREMENTS: Frailty status, assessed at 18-month intervals, was defined using a frailty index (FI) as the number of deficits in 36 health variables. Mobility was defined as time in seconds on the rapid gait test, in which participants walked back and forth over a 20-foot course as quickly as possible. Multistate transition probabilities were calculated with baseline frailty, mobility, age, and sex estimated using Poisson and logistic regressions in survivors and those who died, respectively. RESULTS: In multivariable analyses, baseline frailty status and age were significantly associated with changes in frailty status and risk of death, whereas mobility was significantly associated with the frailty but not with mortality. At all values of the FI, participants with better mobility were more likely than those with poor mobility to remain stable or to improve. For example, at 54 months, 20.6% (95% confidence interval (CI)=16-25.2) of participants with poor mobility had the same or fewer deficits, compared with 32.4% (95% CI=27.9-36.9) of those with better mobility. CONCLUSION: A multistate transition model effectively measured the probability of change in frailty status and risk of death. Mobility, age, and baseline frailty were significant factors in frailty state transitions.