OBJECTIVES

To identify the optimal cutoff points for poor physical function [measured by a 5-times sit-to-stand (5-STS) test] associated with slowness in community-dwelling older adults and to validate the 5-STS cut points by determining whether they predicted future slowness and clinically relevant health outcomes over a 2-year-follow-up period.

DESIGN

Cross-sectional and longitudinal analyses of a cohort study.

SETTING AND PARTICIPANTS

We conducted cross-sectional (n = 2977) and prospective 2-year follow-up analyses (n = 2515) among participants aged 70-84 years enrolled in the nationwide Korean Frailty and Aging Cohort Study (KFACS).

METHODS

Classification and regression tree (CART) analysis was used to identify the 5-STS cut points for poor performance in terms of slowness (eg, gait speed ≥1.0 m/s, gait speed >0.8 m/s and <1.0 m/s, gait speed ≤0.8 m/s) at baseline. Multinomial logistic regression models were used to evaluate the prevalence and incidence of slowness and clinical outcomes according to the three 5-STS categories (normal, intermediate, and poor) in the cross-sectional and longitudinal analyses.

RESULTS

The overall prevalence of slowness in our study sample was 9.0% for a gait speed of ≤0.8 m/s and 32.1% for a gait speed of <1.0 m/s. The CART model identified 5-STS cut points of 10.8 seconds and 12.8 seconds for intermediate and poor physical function, respectively. In the adjusted model, the cut point of 12.8 seconds had a significantly increased likelihood of incident slowness and clinically relevant health outcomes (ie, mobility limitation, disability, frailty, sarcopenia risk, and falls) over the 2-year-follow-up period (all, P < .05).

CONCLUSIONS AND IMPLICATIONS

Our study established 5-STS test cutoff points for poor physical function. Thresholds of 10.8 and 12.8 seconds (intermediate and poor physical function, respectively) for a 5-STS test might help identify individuals at risk of physical function impairments and, thus, help design preventive interventions in community health care settings.