Background: This cross-sectional study was performed to examine associations of objectively measured sedentary time (ST) and breaks in sedentary time (BST) with instrumental activities of daily living (IADL) disability in Japanese community-dwelling older adults. Methods: The sample comprised 1634 older adults (mean age: 73.3 y, men: 38.4%). Sedentary behavior was measured using a triaxial accelerometer. Disability was defined as inability in at least 1 of the IADL tasks using the Tokyo Metropolitan Institute of Gerontology Index of Competence. Results: After adjusting for potential confounders and moderate-to-vigorous physical activity (MVPA), longer ST was significantly associated with higher likelihood of IADL disability, whereas a greater number of BST was associated with lower likelihood of IADL disability. ST and BST remained statistically significant after mutual adjustment with odds ratio of 1.30 (95% confidence interval [CI)], 1.00-1.70) and 0.80 (95% CI, 0.65-0.99), respectively. Conclusions: This study first demonstrated that shorter ST and more BST were associated with lower risk of IADL disability independent of MVPA and that the association for ST was independent of BST and vice versa. These findings suggest not only total ST but also the manner in which it is accumulated may contribute to the maintenance of functional independence in older adults.
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