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Background Deteriorated skeletal muscle condition, including sarcopenia, is a risk factor for disability in older adults. Promoting physical activity is a useful treatment for sarcopenia. However, optimal intensity of physical activity according to sarcopenia characteristics is unclear. Methods This longitudinal cohort study enrolled 2149 community‐dwelling older adults (women 55.7%, mean age: 75.5 ± 4.0 years). Five‐year disability incidence defined by Japanese long‐term care insurance certification and accelerometer‐measured physical activities (light‐intensity physical activity [LPA] and moderate‐to‐vigorous intensity physical activity [MVPA]), which were adjusted for potential confounders, was analysed using cox‐proportional hazard model stratified by sarcopenia characteristics based on the diagnostic algorithm by the Asian working group for sarcopenia (robust, low physical function, low muscle mass, and sarcopenia). The sarcopenia group was defined as low muscle mass and low physical function (weakness and/or slowness). The low muscle mass and low physical function groups were each defined by these characteristics alone. Muscle mass was analysed via bioelectrical impedance analysis. Each intensity of physical activity times was divided by median values. Results The disability incidence rate was 15.4%, excluding those who could not be followed up. Mean LPA times were 43.8 ± 18.0, 45.6 ± 17.5, 45.4 ± 16.6, 40.8 ± 18.6, and 41.4 ± 18.5 min/day and MVPA times were 24.6 ± 17.6, 26.3 ± 18.3, 27.2 ± 17.3, 21.6 ± 16.3, and 21.5 ± 16.4 min/day in all participants, the robust, low muscle mass, low physical function, and sarcopenia groups, respectively. For all participants, higher MVPA was associated with disability incidence [hazard ratios (HR), 0.63; 95% confidence interval (95% CI), 0.49–0.81; P

Gait speed is an important indicator of functional decline in older adults. Recently, daily gait speed has been assessed using accelerometers. However, it is unclear whether this parameter can predict the decline in functional abilities. This study investigates whether daily gait speed can be a predictor of incident disability risk as well as in-laboratory gait speed. A sample of 1860 older adults (Male: 728, Female: 1132; 70.1 ± 6.2 years) were instructed to wear accelerometers on the waist. The association between daily gait speed for two weeks and incident disability during a two-year period was analyzed by using the cut-off value for screening prefrailty in the previous study (106.3 cm/s). Furthermore, the associations with in-laboratory gait speed (cut-off value: 100 cm/s), number of steps (cut-off value: 6342.2 steps/day), and incident disability were also analyzed. Cox proportional hazards analysis showed a significant hazard ratio of low daily gait speed (HR, 2.97; p = 0.02) comparable to that of low in-laboratory gait speed (HR: 2.53; p = 0.01). Conversely, the number of steps had no significant association with incident disability (HR: 1.99; p = 0.12). These results suggest that daily gait speed can be a predictor of incident disability risk in older adults.

Prefrailty is an intermediate stage between non-frailty and frailty. It is associated with an increased risk of progression to frailty, which makes it important to screen older adults for prefrailty at an early stage. This study verified whether daily gait speed and number of steps measured using a tri-axial accelerometer could be used to identify prefrailty. In total, 1692 Japanese community-dwelling older adults were divided into robust (n = 1032) and prefrail (n = 660) groups based on the Kihon Checklist, which is a self-administered questionnaire. Both daily gait speed and number of steps were measured for two weeks using tri-axial accelerometers. We also calculated the area under the ROC curve and the cut-off values for these parameters. Our results showed that the cut-off value for daily gait speed was 106.3 cm/s, while that for number of steps was 6342.2. In addition, we found that the combined assessment of both cut-off values was a more effective way to screen older adults with prefrailty status compared to either parameter alone. This is also considered an effective way to reduce national expenditures for daily care assistance.

Gait speed in laboratory settings (in-laboratory gait speed) is one of the important indicators associated with the decline in functional abilities in older adulthood. Recently, it has become possible to measure gait speed during daily living (daily gait speed) using accelerometers. However, the relationship between these two gait speed parameters is unclear. This study aimed to compare in-laboratory gait speed, measured by a sheet-type pressure sensor, and daily gait speed, measured by an accelerometer, in healthy community-dwelling older adults. Participants were aged ≥60 years, residing in Takahama city, Aichi, Japan. To calculate daily gait speed, participants were instructed to wear a tri-axial accelerometer on their waist. A total of 1965 participants were included in the final analysis. The results showed a weak association (r = 0.333, p

Objective The purpose of the study was to estimate, using an isotemporal substitution model, the effect of replacing sedentary behavior (SB) with physical activity on the incidence of disability in community-dwelling older adults. Methods This 2-year longitudinal cohort study enrolled 3691 community-dwelling older adults (57.2% women; mean age = 74.0 [SD = 5.0] years). Individuals with dementia, stroke, Parkinson disease, depression, low Mini-Mental State Examination scores, dependence on basic activities of daily living, and missing data were excluded. Physical activity and potential confounding factors were investigated as a baseline survey of disability incidence, defined by Japanese long-term care insurance certification, for 2 years in 2 regions. Physical activity data (SB, light-intensity physical activity, and moderate- to vigorous-intensity physical activity [MVPA]) were measured using triaxial accelerometers for 14 days, and daily mean time spent in each physical activity parameter was computed in increments of 10 minutes. The relationship between baseline physical activity and disability incidence adjusted for potential confounders was analyzed using multilevel Cox proportional hazards regression analyses with an isotemporal substitution model. Results The disability incidence rate was 3.8%, excluding individuals who could not be followed-up. Replacing 10 minutes of SB per day with MVPA was associated with a decreased disability incidence (hazard ratio = 0.870; 95% CI = 0.766–0.988), whereas no evidence was found for replacing SB with light-intensity physical activity (hazard ratio = 0.980; 95% CI = 0.873–1.10). Conclusions Replacing SB with MVPA was associated with a lower risk of disability. These findings are helpful for establishing disability prevention strategies. Impact These results suggest that feasible changes in daily behavior, such as replacing 10 minutes of SB with MVPA daily, might have a protective effect on disability incidence. Clarifying these associations is useful for developing disability prevention strategies and may help reduce the incidence of disability in community-dwelling older adults.