Does long-term experience of nonstandard employment increase the incidence of depression in the elderly?

OBJECTIVES: Our prospective study aimed to elucidate the effect of long-term experience of nonstandard employment status on the incidence of depression in elderly population using the Korean Longitudinal Study of Ageing (KLoSA) study. METHODS: This study used the first- to fourth-wave cohorts of KLoSA. After the exclusion of the unemployed and participants who experienced a change in employment status during the follow-up periods, we analyzed a total of 1,817 participants. Employment contracts were assessed by self-reported questions:standard or nonstandard employment. The short form of the Center for Epidemiologic Studies Depression Scale (CES-D) served as the outcome measure. Hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated using Cox proportional hazards models to evaluate the association between standard/nonstandard employees and development of depression. RESULTS: The mean age of the participants was 53.90 (±7.21) years. We observed that nonstandard employment significantly increased the risk of depression. Compared with standard employees, nonstandard employees had a 1.5-fold elevated risk for depression after adjusting for age, gender, CES-D score at baseline, household income, occupation category, current marital status, number of living siblings, perceived health status, and chronic diseases [HR=1.461, 95% CI= (1.184, 1.805) ]. Moreover, regardless of other individual characteristics, the elevated risk of depression was observed among all kinds of nonstandard workers, such as temporary and day workers, full-time and part-time workers, and directly employed and dispatched labor. CONCLUSIONS: The 6-year follow-up study revealed that long-term experience of nonstandard employment status increased the risk of depression in elderly population in Korea.