Associations of 24-hour movement behaviors with functional disability in Chinese community-dwelling older adults: a compositional isotemporal substitution analysis

Evidence on the associations of 24-hour movement behaviors with functional disability in Chinese community-dwelling older adults remains limited. Using a compositional isotemporal substitution analysis, this study examined these associations and the theoretical effects of reallocating time between movement behaviors on functional disability. A total of 239 community-dwelling older adults wore wrist-worn ActiGraph GT3X-BT accelerometers for seven days to objectively assess sedentary behavior (SB), light-intensity physical activity (LPA), moderate-to-vigorous physical activity (MVPA), and sleep period (SP). Functional disability was quantified via the Katz Index of Independence in Activities of Daily Living (ADL) and the Lawton Instrumental Activities of Daily Living (IADL) Scale. Compositional data analysis (CoDA) and isotemporal substitution models were employed to examine the associations of 24-hour movement behaviors with functional disability. The 24-hour movement composition was significantly associated with functional disability (ADL and IADL; all P < 0.01; adjusted R ² = 0.29 and 0.26, respectively). MVPA was positively associated with ADL, whereas SB was negatively associated with ADL; LPA was not significantly associated with ADL. SP was marginally associated with better IADL. Reallocating 15 min from SB to MVPA was associated with increases of 0.324 and 0.393 points in ADL and IADL, respectively. A 15-min proportional reallocation of time to MVPA from sleep, SB, and LPA was associated with improvements in ADL by 0.299 points and IADL by 0.340 points. Substitution effects were asymmetric, with MVPA reductions being associated with larger declines than equivalent increases in MVPA, whereas other reallocations had minimal estimated effects. The compositional distribution of 24-hour movement behaviors was significantly associated with functional disability in Chinese community-dwelling older adults, with MVPA showing a favorable association and SB showing an adverse association. Reallocating time from other behaviors, particularly SB, to MVPA was associated with favorable predicted changes in ADL and IADL scores within the observed range of function These findings provide scientific evidence for developing targeted movement behavior intervention strategies for older adults. Not applicable.