The aim of this study is to examine a relationship between a change in social activity and depression among Koreans aged 45 years or more.

Data came from the Korean Longitudinal Study of Aging (KLoSA) (2006–2010), with 5,327 participants aged 45 years or more. The generalized estimating equation (GEE) with the logit link was used to investigate an association between a change in social activity during 2006–2008 (or 2008–2010) and depression among respondents in year 2008 (or Y2010). Depression was measured by Center for Epidemiological Studies Depression scale (CES-D10) and a change in social activity was classified with four categories, i.e. “consistent participation”, “consistent non-participation”, “participation to non-participation”, and “non-participation to participation”. Social activity was divided into various elements and the same analysis was conducted for each of these elements.

Those with consistent non-participation and from participation to non-participation were more likely to be depressed than those with consistent participation and from non-participation to participation in social activities (OR 1.44 [95% CI 1.22–1.71], OR 1.35 [95% CI 1.15–1.58] vs. OR 1.00 [Reference], OR 1.27 [95% CI 1.09–1.48]). In addition, the strength of the negative association between consistent or new participation in social activity and depression was different across different elements of social activity. The negative association was particularly strong for leisure, culture or sports clubs, and for family or school reunion.

For improving the mental health of the population aged 45 years or more, the promotion of their continued or new participations in leisure/culture clubs and family/school reunion might be needed in South Korea.