The risk of suicide mortality according to income dynamics assessed using health insurance premium data: A nationwide cohort study in Korea.

Low income is a known risk factor for suicide; however, how changes in income and its fluctuation relate to suicide risk remains unexamined. Using the Korean National Health Insurance Service database, 4,031,867 adults aged 30 years or older who underwent a health checkup in 2012 were followed until the end of 2022. Based on health insurance premiums, income levels and changes between 2008 and 2012 were assessed. Low-income status was defined as the lowest quartile or receiving Medical Aid. Income variability was the standard deviation of the percentage change in income over five years. Hazard ratios (HRs) and 95 % confidence intervals (CIs) for suicide were calculated using multivariable Cox regression. During a 9.2-year follow-up, 10,012 suicide deaths (0.25 %) occurred. Persistent low income for five years was associated with a 48 % increased suicide risk (HR 1.48, 95 % CI 1.38-1.58) compared with those never in low income. Conversely, persistent high income was associated with a decreased suicide risk (HR 0.67, 95 % CI 0.64-0.71). Income decreases resulting in low-income status (HR 1.26, 95 % CI 1.12-1.43) and high variability in income (HR 1.37, 95 % CI 1.29-1.45) were also associated with increased suicide risk. These patterns were consistent regardless of the presence of depression and disability but were more pronounced in males and those under 65. In conclusion, persistent low-income, income decreases, and high variability were all independently associated with increased suicide risks. Suicide prevention strategies should promote income stability while accounting for age and sex.