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  • Author: Shuzo Kumagai x
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Tao Chen, Kenji Narazaki, Yuka Haeuchi, Sanmei Chen, Takanori Honda and Shuzo Kumagai


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.


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.


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.


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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Koji Yonemoto, Takanori Honda, Hiro Kishimoto, Daigo Yoshida, Jun Hata, Naoko Mukai, Mao Shibata, Yoichiro Hirakawa, Toshiharu Ninomiya and Shuzo Kumagai

Background: The purpose of this study was to describe changes in physical activity volumes and sedentary time over 3 years in the middle-aged and older Japanese population. Methods: Study participants included 1151 Japanese community-dwelling residents aged ≥40 years in 2009 who underwent 2 sets of health examinations (2009 and 2012). Using a triaxial accelerometer, longitudinal changes in sedentary time, light physical activity volume, moderate to vigorous physical activity volume, number of steps, and total physical activity volume were evaluated according to sex, age (40–49, 50–59, 60–69, 70–79, and ≥80 y), and obese (nonobese and obese) categories. Results: Sedentary time significantly increased, and all physical activity volumes significantly decreased among all participants. Although most variables did not change significantly in the 40–49 and 50–59 year age categories, similar changes as all participants were observed across all other categories. In the correlation analyses, changes in sedentary time correlated, at most, only modestly for each change in physical activity volumes, indicating that increased physical activity volume does not always lead to decreased sedentary time, and vice versa. Conclusions: Strategies to reduce sedentary time and promote physical activity are needed in Japan, particularly for people aged ≥60 years.