title: Synergistic effect of interaction between perceived health and social activity on depressive symptoms in the middle-aged and elderly: a population-based longitudinal study.
abstract: OBJECTIVE
  To examine the synergistic effect of interaction between perceived health and social activity on depressive symptoms.
  
  
  METHODS
  We investigated whether the interaction between perceived health and social activity has a synergistic effect on depressive symptoms in the middle-aged and elderly using data from 6590 respondents aged 45 and older in the Korean Longitudinal Study on Aging (KLoSA), 2006-2012. A generalised linear mixed-effects model was used to investigate the association in a longitudinal data form. Depressive symptoms were measured using the Center for Epidemiological Studies Depression 10 Scale (CES-D10). Perceived health and level of social activity were categorical variables with three values. Participation in six social activities was assessed.
  
  
  RESULTS
  Interactions between perceived health status and social activity were statistically significant for almost all social activity/perceived health combinations. Addition of the interaction term significantly decreased CES-D10 scores, confirming the synergistic effect of the interaction between perceived health status and social activity ('normal×moderate', β=-0.1826; 'poor×moderate', β=-0.5739; 'poor×active', β=-0.8935). In addition, we performed stratified analyses by region: urban or rural. In urban respondents, the additional effect of the interaction term decreased CES-D10 scores and all social activity/perceived health combinations were statistically significant ('normal×moderate', β=-0.2578; 'normal×active', β=-0.3945; 'poor×moderate', β=-0.5739; 'poor×active', β=-0.8935). In rural respondents, only one social activity/perceived health combination was statistically significant, and the additional effect of the interaction term showed no consistent trend on CES-D10 scores.
  
  
  CONCLUSIONS
  The interaction between perceived health and social activity has a synergistic effect on depressive symptoms; the additional effect of the interaction term significantly decreased CES-D10 scores in our models.
authors.affiliation: Department of Public Health, Graduate School, Yonsei University, Seoul, Republic of Korea Institute of Health Services Research, Yonsei University, Seoul, Republic of Korea.
authors.forename: Sung-Youn
authors.initials: SY
authors.lastname: Chun
authors.affiliation: Department of Public Health, Graduate School, Yonsei University, Seoul, Republic of Korea Institute of Health Services Research, Yonsei University, Seoul, Republic of Korea.
authors.forename: Kyu-Tae
authors.initials: KT
authors.lastname: Han
authors.affiliation: Institute of Health Services Research, Yonsei University, Seoul, Republic of Korea Department of Health Policy and Management, Graduate School of Public Health, Yonsei University, Seoul, Republic of Korea.
authors.forename: Seo Yoon
authors.initials: SY
authors.lastname: Lee
authors.affiliation: Department of Public Health, Graduate School, Yonsei University, Seoul, Republic of Korea Institute of Health Services Research, Yonsei University, Seoul, Republic of Korea.
authors.forename: Chan Ok
authors.initials: CO
authors.lastname: Kim
authors.affiliation: Institute of Health Services Research, Yonsei University, Seoul, Republic of Korea Department of Preventive Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Eun-Cheol
authors.initials: EC
authors.lastname: Park
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003863:Depression / Q000523:psychology*; D005260:Female; D006304:Health Status; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D008960:Models, Psychological; D011569:Psychiatric Status Rating Scales; D056910:Republic of Korea; D012424:Rural Population; D058992:Social Participation / Q000523:psychology*; D014505:Urban Population
keywords: GERIATRIC MEDICINE; MENTAL HEALTH; PUBLIC HEALTH; SOCIAL MEDICINE