Incidence of stroke in relation to cognitive function and dementia in the Kungsholmen project

Objective: To investigate whether cognitive function is related to incidence of stroke. Methods: A population-based cohort of 1551 subjects with no clinical history or signs of stroke, age 75 years and over at baseline, were followed up for 3 years. Individuals with a first-ever stroke event that was recorded in the Stockholm inpatient register after the date of baseline interview were considered as incident stroke patients. Diagnosis of stroke followed the International Classification of Disease, 9th Revision (ICD-9). Diagnosis of dementia was made according to the Diagnostic and Statistical Manual of Mental Disorders, 3rd ed., revised (DSM-III-R). Cognitive functioning was assessed with the Mini-Mental State Examination. Results: During the 4102 person-years of follow-up, 110 events were recorded, giving an overall incidence of stroke of 26.8 per 1000 person-years. Subjects with mild dementia had a relative risk of 2.6 (95% CI, 1.2 to 5.7) of developing stroke after controlling for the potential confounders. The corresponding figure for subjects with cognitive impairment was 2.0 (95% CI, 1.0 to 3.8; p = 0.05). There was a tendency for subjects who developed stroke to be more likely to have vascular factors (systolic blood pressure >180 mm Hg, heart disease, or diabetes mellitus) than those who did not. Conclusions: Mild dementia and cognitive impairment are associated with an increased incidence of stroke among subjects age 75 years old and over. Because stroke increases risk of dementia and prior stroke increases risk of a subsequent stroke, mild dementia and cognitive impairment may be a manifestation of clinically unrecognized stroke.