Abstract
BACKGROUND: The interaction and substitution effects of physical activity (PA) and sitting time (ST) living in non-western countries have not been well investigated. This study aimed to examine the association of moderate-to-vigorous physical activity (MVPA) and ST with disability and mortality in older adults. METHODS: This prospective study analyzed data from 10,164 adults aged over 65 years who participated in the Kyoto-Kameoka study in Japan. We evaluated MVPA and ST using the validated International Physical Activity Questionnaire-Short Form. Participants were categorized into four groups based on their levels of MVPA (150 min/week) and ST (300 min/day): low MVPA/high ST, low MVPA/low ST, high MVPA/high ST, and high MVPA/low ST. Outcomes were gathered between July 30, 2011, and November 30, 2016. RESULTS: Over a median follow-up of 5.3 years (45,461 person-years), 2,273 disability cases were documented. The low MVPA/high ST groups were associated with higher disability risk than those in the high MVPA/low ST groups (hazard ratio [HR] 1.52; 95% confidence interval [CI], 1.31-1.75), and the interaction between MVPA and ST accounted for 48.5% of the relative excess risk of disability in the low MVPA/high ST group (P for interaction = 0.006). Daily replacement of 10 minutes of ST with 10 minutes of MVPA was associated with a reduced risk of disability (HR 0.980; 95% CI, 0.971-0.989) and all-cause mortality (HR 0.975; 95% CI, 0.962-0.988). CONCLUSION: These findings indicate that even a small substitution of ST with MVPA could help lower both the risk of disability and mortality.