Ischemic stroke incidence, severity heightens risk for dementia

Among participants in a decades-long prospective cohort study, risk for dementia significantly increased after ischemic stroke, according to results published in JAMA Neurology.

“Risk of dementia increases after stroke and may be especially high in patients with larger and more severe strokes,” Silvia Koton, PhD, RN, professor of nursing in the Stanley Steyer School of Health Professions at Tel Aviv University, and colleagues wrote. “Reliable estimates for the risk of dementia after stroke (especially ischemic stroke, which is the most common type) are needed to inform clinicians, researchers and policymakers.”

Researchers, seeking to examine the risk for dementia following ischemic stroke (IS) and assess the impact of stroke severity and recurrence, monitored 15,379 individuals who were free from stroke and dementia from 1987 to 1989. Participants, aged 45 to 64 years, were part of a cohort in the Atherosclerosis Risk in Communities study, which spans Mississippi, Maryland, Minnesota and North Carolina. Koton and colleagues evaluated participants and studied associations between diagnosis of dementia and IS incidence, frequency and severity at baseline and at six additional visits, at 1- to 2-year intervals, through 2019.

Investigators reviewed hospital records to classify initial and recurrent IS and measured severity with the NIH Stroke Scale (minor, 5; mild, 6-10; moderate, 11-15; and severe, 16). They determined dementia cases by reviewing in-person evaluations, telephone-based assessments, hospitalization codes and death certificates.

According to study results, 1,378 (1,155 incident) IS and 2,860 dementia cases were diagnosed 1 year or more after incident stroke in participants with stroke, or at any point after baseline in participants without stroke. Of the dementia cases, 269 had a preceding IS, and the median time between ischemic stroke and dementia was 7.2 years. Compared with participants with no stroke, the risk for dementia was highest for those who suffered two or more moderate to severe strokes, followed by those with two or more mild strokes and those who had one moderate to severe stroke. The risk was lowest for those with one minor to mild stroke.

“Despite decreases in stroke incidence rates over time, dementia remains a major concern

for individuals with a prior stroke,” Koton and colleagues wrote. “Because both stroke severity and recurrent stroke are associated with an elevated risk of dementia, this emphasizes the importance of not only prevention of stroke incidence but also secondary prevention to reduce stroke recurrence.”