Associations of depressive symptoms and instrumental activities of daily living decline by employment or participation in social activities among younger-older Japanese in the New Integrated Suburban Seniority Investigation (NISSIN) Project

Objectives This study investigated the association between depressive symptoms and the instrumental activities of daily living (IADL) decline among physically and socially independent older people according to being employed or participating in social activities in a Japanese age-specific cohort. Methods We performed a prospective cohort study including 1,508 (716 men and 792 women) aged 64/65. Depressive symptoms were assessed at baseline (2000–2005). The change in IADL status was ascertained in the secondary survey when the participants reached 70 years of age. Multivariable odds ratios (ORs) and confidence intervals (CIs) of depressive symptoms for IADL decline were calculated using a logistic regression model adjusted for enroll year, sex, employment status, marital status, education, smoking status, alcohol consumption status, body mass index, walking status, daily sleep duration, and medical histories of cancer, cardio-cerebrovascular diseases, hypertension, and diabetes mellitus. We also formally tested for potential interaction effects by employment and participation in social activities. Results The OR of the presence of depressive symptoms and not employed was 3.25 (95% CI 1.57–6.75), compared to participants without depressive symptoms and employed, after adjusting for potential confounders. Compared to participants without depressive symptoms and with a high frequency of participation in social activities, participants with depressive symptoms and a low frequency of participation in social activities were associated with IADL decline (OR 2.45; 95% CI 1.23–4.90). However, we observed no evidence of an interaction effect by employment and participation in social activities. Conclusions This age-specific cohort study revealed that being employed or participating in social activities may prevent IADL decline among depressed older adults.