Risk of Suicide in Association with Major Depressive Disorder among Patients with Dementia: A Population-based Nested Case-Control Study.

Objective: This study aimed to explore the association between major depressive disorder (MDD) and suicide risk in dementia patients.

Methods: A cohort of 625,218 individuals aged ≥40 years with dementia between 2007 and 2018 was identified from Taiwan's National Health Insurance Research Database. After excluding prevalent cases in 2007. Subsequently, a nested case-control study enrolled 1,256 suicide cases and 5,022 matched controls was conducted. The frequencies of MDD-related outpatient or inpatient visits over a 7-year period preceding the event dates were calculated and analyzed for association using conditional logistic regression.

Results: Dementia comorbid with MDD was associated with increased suicide risk (adjusted odds ratio [AOR]: 2.67), particularly in individuals with ≤1.0 MDD episodes per year (AOR: 2.85). Similar association was observed only in individuals aged ≥65 years and males, with a pronounced risk of suicide in those ≤1.0 MDD episodes per year (AOR: 3.08 for individuals aged ≥65 years; AOR: 3.28 for males). Conversely, the risk increase was evident with >1.0 MDD episodes per year in those aged <65 years (AOR: 3.04) and females (AOR: 2.45).

Conclusions: MDD is associated with suicide risk in dementia patients, with the strength of this association possibly varying by age and gender.