Cross-sectional associations of sedentary behaviour and physical activity on depression in Japanese older adults: an isotemporal substitution approach

Objectives: Reducing sedentary behaviour (SB) and increasing physical activity (PA) have been shown to be associated with decreased depression. However, there are yet few studies examining the potential benefits on older adults’ depression, when SB is replaced with PA. This study aimed to examine the associations of objectively assessed SB, light-intensity PA (LPA) and moderate-to-vigorous PA (MVPA) with depression among a sample of Japanese older adults, and to explore impacts of substituting SB with PA on older adults’ depression. Design: Cross-sectional analysis. Setting: General community. Participants: A total of 276 older adults aged 65–85 years living in Japan. Main outcome measures: Three behaviours including the average daily time spent in SB (≤1.5 METs); LPA ( > 1.5 to < 3.0 METs) and MVPA (≥3.0 METs) per day were calculated by accelerometers. Depression was assessed using the Japanese version of the 15-item Geriatric Depression Scale (GDS-15). Results: Less SB (β=0.129, 95% CI 0.015 to 0.243) and more LPA (β=−0.138, 95% CI −0.265 to −0.011) were found to be significantly and negatively associated with the GDS-15 score in the single-activity model. The isotemporal substitution model found that replacing only 30 min per day of SB with the same amount of LPA to be significantly and negatively associated with the GDS-15 score (β=−0.131, 95% CI −0.260 to −0.002). Conclusions: These findings indicated that substituting even small amounts of SB with LPA may contribute to less depression in older adults. Potential favourable effects can be observed for replacing only 30 min per day of SB with LPA