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Abstract Background Previous studies have examined associations between sitting time and negative health outcomes and mental health. However, the relationship between overall sitting time and major depressive disorder (MDD) in South Korea has not been studied. This study examined the association between MDD and overall sitting time and physical activity in South Koreans. Methods Data from the sixth Korean National Health and Nutrition Examination Survey (KNHANES), a cross-sectional, nationally representative survey, were analyzed. Total participants were 4145 in 2014. MDD was assessed using the Patient Health Questionnaire (PHQ-9). Participants’ data regarding self-reported sitting time and physical activity were analyzed via multiple logistic regression. Results Results showed that people who sat for 8–10 h (OR: 1.56, 95% CI: 1.15–2.11) or more than 10 h (OR: 1.71, 95% CI: 1.23–2.39) had increased risk of MDD compared to those who sat for less than 5 h a day. Subgroup analysis showed that the strongest effect of reported sitting time on risk of MDD was found in men with lower levels of physical activity who sat for 8 to 10 h (OR: 3.04, 95% CI: 1.15–8.01) or more than 10 h (OR: 3.43, 95% CI: 1.26–9.35). Level of physical activity was not an independent predictor for MDD. Conclusions Sitting for long periods was associated with greater risk of MDD in South Korean adults. Reducing sitting time in people with MDD could help to prevent associated physical health problems and may improve mental health.

Background: Numerous studies suggesting the relation between self-rated health (SRH) and depression have been reported using different measures. Therefore, we attempted to determine the difference in a depressive scale based on the different ways of measuring health between global SRH (SRH-global) and age-comparative SRH (SRH-age). Then, the combined effect of SRH-global and SRH-age on depressive symptoms was further investigated. Methods: Data from the Korean Longitudinal Study of Ageing (KLoSA) from 2008 to 2012 were analyzed. We divided the SRH-global and SRH-age into three levels--high, middle, and low--and combined each into nine new categories (SRH-combi). The Center for Epidemiologic Studies Depression Scale-10 Korean edition was used as the dependent variable. Results: A total of 8621 participant were enrolled at baseline. Individuals with lower SRHs-age compared to SRH-global tended to be more vulnerable to depressive symptoms. Low SRH-global with low (b = 0.654, p < 0.001) and middle SRH-age (b = 0.210, p = 0.003) showed association with higher CESD scores. Participants with high SRH-global × low SRH-age also had higher scores (b = 0.536, p < 0.001) compared to the "middle SRH-global × middle SRH-age" reference group. In contrast, among the middle (b = -0.696, p < 0.001) and high SRH-global (b = -0.545, p < 0.001) groups, participants with superior SRH-age had statistically lower CESD scores than the reference group. Conclusions: Although a sole general SRH has historically been widely used, it has been suggested that use of both general and age-comparative SRH would be more powerful and easy when we consider analyzing depression in old age. [ABSTRACT FROM AUTHOR]