Suicide rates across income levels: Retrospective cohort data on 1 million participants collected between 2003 and 2013 in South Korea

BACKGROUND The relation of income and socioeconomic status with suicide rates remains unclear. Most previous studies have focused on the relationship between suicide rates and macroeconomic factors (e.g., economic growth rate). Therefore, we aimed to identify the relationship between individuals' socioeconomic position and suicide risk. METHODS We analyzed suicide mortality rates across socioeconomic positions to identify potential trends using observational data on suicide mortality collected between January 2003 and December 2013 from 1,025,340 national health insurance enrollees. We followed the subjects for 123.5 months on average. Socioeconomic position was estimated using insurance premium levels. To examine the hazard ratios of suicide mortality in various socioeconomic positions, we used Cox proportional hazard models. RESULTS We found that the hazard ratios of suicide showed an increasing trend as socioeconomic position decreased. After adjusting for gender, age, geographic location, and disability level, Medicaid recipients had the highest suicide hazard ratio (2.28; 95% CI, 1.87-2.77). Among the Medicaid recipients, men had higher hazard ratios than women (2.79; 95% CI, 2.17-3.59 vs. 1.71; 95% CI, 1.25-2.34). Hazard ratios also varied across age groups. The highest hazard ratio was found in the 40-59-year-old group (3.19; 95% CI, 2.31-4.43), whereas the lowest ratio was found in those 60 years and older (1.44; 95% CI, 1.09-1.87). CONCLUSIONS Our results illuminate the relationship between socioeconomic position and suicide rates and can be used to design and implement future policies on suicide prevention.