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

Abstract

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 community-dwelling 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.

Figure 1

Changes in frailty status (deficit count) in relation to baseline mobility for three consecutive follow-up assessments. The probability of improvement or stability is indicated in white, worsening is shown in grey, and probability of death is shown in black. The probabilities of the outcomes among participants with poor mobility (>10 sec on rapid gait test) are shown at the left panels; the probabilities of the outcomes among participants with good mobility are presented at the right panels. The upper panels show the transition probabilities after the first 18 months, the middle panels displays the probabilities of transitions between baseline and 36 months and the bottom panel shows the probabilities between baseline and 54 months. The last state (10+) refers to the “collapsed states” for those who had 10 deficits and over (<8%).