Stroke Recurrence & Severity Increases Risk of Dementia: ARIC Study

The researchers included 15,379 patients from the ongoing Atherosclerosis Risk in Communities (ARIC) study who were free of stroke and dementia at baseline (1987 to 1989) with follow-up through December 2019. They assessed the link between dementia and ischemic stroke incidence, frequency, and severity, over a median follow-up of 25.5 years and a mean of 4.4 visits. The major outcome assessed was the incidence of dementia. However, for patients with stroke, dementia incidence in the first year after stroke was not counted.

Key findings of the study:

• Among 1,155 incident strokes identified in follow-up, the researchers classified severity by the National Institutes of Health Stroke Scale (NIHSS) as minor (NIHSS 5 or less, 62.8%); mild (NIHSS 6-10, 22.1%); moderate (NIHSS 11-15, 7.9%); or severe (NIHSS 16 or more, 7.1%).
• They observed 2,860 dementia cases, which included those with incident stroke diagnosed 1 year or more after the stroke, as well as dementia diagnosed any time after baseline in those without stroke.
• Upon analysis, they found that the risk of dementia increased with both the number and severity of strokes. Also, the risk was correlated with stroke severity and the number of stroke events in a dose-dependent manner.
• Compared with no stroke, they noted that the risk of dementia 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.

The authors concluded, " In this study, risk of dementia significantly increased after ischemic stroke, independent of vascular risk factors. Results suggest a dose-response association of stroke severity and recurrence with risk of dementia."

For further information:

DOI:10.1001/jamaneurol.2021.5080.