Following ischemic stroke, a significant increase in the risk of dementia was evident independent of vascular risk factors. Findings indicate a dose-response association of stroke severity and recurrence with risk of dementia.

• A total of 15,379 participants in the Atherosclerosis Risk in Communities (ARIC) study who were free of stroke and dementia at baseline (1987 to 1989) were monitored through 2019 to investigate the risk of dementia following incident ischemic stroke and examine how it varied by stroke severity and recurrence.

• In this cohort, 1,378 ischemic strokes and 2,860 incident dementia cases occurred.

• Risk of dementia rose with both the number and severity of strokes.

• Relative to no stroke, dementia risk by adjusted hazard ratio was 1.76 for 1 minor to mild stroke, 3.47 for 1 moderate to severe stroke, 3.48 for 2 or more minor to mild strokes, and 6.68 for 2 or more moderate to severe strokes.