Background: To investigate the risk of stroke in patients within 3 years of newly diagnosed Alzheimer`s disease (AD) compared non-AD patients among elderly populations aged 60 and above in South Korea between 2004 and 2013.  
Methods: This retrospective, nationwide, longitudinal population-based study used National Health Insurance Service-National Elderly cohort (NHIS-elderly) Database to define patients with AD from 2004 to 2013 based on having KCD (Korean Classification of Diseases) code G30 and F00. We performed a 1:5 case-control matched analysis using propensity score matching, which were based on age, sex and household income. We conducted Cox proportional hazards regression analysis to estimate the risk of ischemic and hemorrhagic stroke in AD.
Results: AD patients have a greater risk of developing stroke than those without AD. In the cohort study, the adjusted hazard ratios (HRs) for total stroke, ischemic stroke and hemorrhagic stroke were 2.87 (95% CI, 2.707-3.042), 2.546 (95% CI, 2.393-2.709) and 1.998 (95% CI, 1.624-2.458), respectively.
Conclusions: Our data show that AD is significantly increased risk of stroke development.

Association between Alzheimer disease and risk of stroke: A 11--year nationwide cohort study