Depression and Long-term Mortality among 5-year Breast Cancer Survivors in Korea: A Population-based Cohort Study

Background Depression is common and harmful among breast cancer survivors, but it may be neglected and untreated in non-Western settings. We examined the association of depression after breast cancer diagnosis with long-term mortality risk in a Korean cohort. Methods We used data from the National Health Insurance Service cancer patients cohort database of South Korea. We included women aged 40 or older who were diagnosed with breast cancer between 2007 and 2013, survived at least 5 years, and had no depression history. Depression was defined as hospitalization for more than 2 days due to depression (ICD-10 code F22 or F23) after diagnosis. We assessed all-cause, cancer-specific, and non-cancer-specific mortality by Cox proportional hazards model, adjusting for covariates. Results Among 30,371 women (mean [SD] age, 56.5 [11.4] years), 30,371 had depression. During the 5-year period, 1,904 deaths occurred (33.6 per 1,000 person-years). Depression patients had higher risks of all-cause mortality (adjusted hazard ratio [aHR], 1.38; 95% CI, 1.03–1.86) and non-cancer-specific mortality (aHR, 1.81; 95% CI, 1.14–2.86) compared to non-depression patients with Charlson comorbidity index of 2 or more. Cancer mortality was not significantly different. All-cause mortality was also higher for depression patients aged 65 or older (aHR, 1.96; 95% CI, 1.27–3.03). Conclusions Depression was linked to increased mortality among 5-year breast cancer survivors, especially for non-cancer causes. This study implies the need for depression screening and treatment among breast cancer patients, especially in non-Western settings where depression may be underdiagnosed and undertreated.