Background: The literature has shown depression to be associated with an increased risk of dementia. In addition, hormone therapy can be a responsive treatment option for a certain type of depression. In this study, we examined the association between hormone therapy, including lifetime oral contraceptive (OC) use, and hormone replacement therapy (HRT) after menopause with the occurrence of dementia among female patients with depression.Methods: The South Korean national claims data from

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... 1, 2005, to December 31, 2018, was used. Female subjects aged 40 years or older with depression were included in the analyses. Information on hormone therapy was identified from health examination data and followed up for the occurrence of dementia during the average follow-up period of 7.72 years.Results: Among 209,588 subjects, 23,555 were diagnosed with Alzheimer's disease (AD) and 3,023 with vascular dementia (VD). Lifetime OC usage was associated with a decreased risk of AD (OC use for <1 year: HR, 0.92; [95% CI, 0.88–0.97]; and OC use for ≥1 year: HR, 0.89 [95% CI, 0.84–0.94]), and HRT after menopause was associated with a decreased risk of AD (HRT for <2 years: HR, 0.84 [95% CI, 0.79–0.89]; HRT for 2–5 years: HR, 0.80 [95% CI, 0.74–0.88]; and HRT for ≥5 years : HR, 0.78 [95% CI, 0.71–0.85]) and VD (HRT <2 years: HR, 0.82 [95% CI, 0.71–0.96]; HRT for 2–5 years: HR, 0.81 [95% CI, 0.64–1.02]; and HRT for ≥5 years: HR, 0.61 [95% CI, 0.47–0.79]).Conclusions: In this cohort study using national claims data, lifetime OC use was associated with a decreased risk of AD, and HRT after menopause was associated with a decreased risk of AD and VD among people with depression. However, further studies are needed to establish causality.