Incidence and Risk of Stroke following Dementia: A Nationwide Cohort Study in South Korea

Introduction: This study aimed to evaluate the long-term risk of stroke following dementia diagnosis and compare stroke risk across dementia subtypes using nationwide cohort data. Methods: We performed a retrospective cohort study using Korean National Health Insurance Service data (2002–2013). Patients with newly diagnosed dementia (n = 2, 820) were matched 1:10 with controls (n = 28, 200) by age, sex, and health screening year. Stroke incidence was evaluated over up to 10 years of follow-up. Adjusted hazard ratios (aHRs) were calculated using Cox regression. Results: During a mean follow-up of 2.49 years (median, 1.99; standard deviation, 2.07; interquartile range, 2.66), dementia was significantly associated with increased stroke risk (aHR, 3.19; 95% confidence interval, 2.84–3.57). The highest risk was observed in patients with vascular dementia (VaD; aHR, 3.58), followed by Alzheimer’s disease (AD; aHR, 2.73) and other dementias (aHR, 2.61). Ischemic stroke (IS) was more common than hemorrhagic stroke (HS) across all subtypes. The relative risk was greater in individuals aged <60 years and in males with AD or other dementias, whereas sex differences were not evident in VaD. Conclusion: Dementia, especially VaD, is a strong risk factor for both IS and HS. These findings support the need for dementia subtype-specific cerebrovascular risk assessment and long-term prevention strategies.