Background: Associations between levels of sedentary behavior and depressive symptoms independently and in combination with different levels of physical activity remain unclear. Purpose: This study aimed to examine independent and combined associations of physical activity (PA) and sedentary behavior (SB) with depressive symptoms among Japanese adults. Method: An Internet-based survey collected data on depression levels (Center for Epidemiologic Studies Depression Scale), self-reported time spent in PA and SB (Japanese short version of the International Physical Activity Questionnaire), and sociodemographic variables from 2,914 adults in 2009. Binary logistic regression analyses were conducted to examine the odds ratios (ORs) for being depressed (depression scores ≥16) according to independent PA levels (none, insufficient, sufficient), SB levels (low, moderate, high), and nine combinations of PA and SB categories. Results: After adjusting for potential confounders, sufficient PA level was found to be related to lower risk of depressive symptoms independently (OR = 0.61), whereas no significant associations were observed between SB levels and depression. In the combined associations, adults in the sufficient PA/high SB (OR = 0.44), sufficient PA/moderate SB (OR = 0.56), and sufficient PA/low SB (OR = 0.57) categories were significantly less likely to have depressive symptoms in comparison with the no PA/high SB category. Conclusion: Meeting physical activity recommendations is associated with a lower risk of depressive symptoms, regardless of time spent in total sedentary behavior. These results suggest that promoting physical activity may be an effective strategy against depressive symptoms among Japanese adults.
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