"These data emphasize the value of both primary and secondary stroke prevention for reducing dementia risk," researchers write in JAMA Neurology.
The findings are based on 15,379 adults in the ongoing prospective Atherosclerosis Risk in Communities (ARIC) study who were free of stroke and dementia at baseline (1987 to 1989) and were followed through the end of 2019. Their mean age at baseline was 54 years, 55% were women, 73% were white and 27% were Black.
During a median follow-up of nearly 26 years, a total of 1,378 ischemic strokes (1,155 incident strokes) were identified. By the National Institutes of Health Stroke Scale (NIHSS), 63% of strokes were minor, 22% were mild, 8% were moderate and 7% were severe. A total of 2,860 people were diagnosed with dementia during the study period.
Compared with individuals who never had a stroke, and after adjusting for sociodemographic characteristics, APOE status and vascular risk factors, the hazard ratio for dementia was 1.76 (95% CI, 1.49 to 2.00) in individuals with one minor to mild stroke, 3.47 (95% CI: 2.23 to 5.40) in those with one moderate to severe stroke, 3.48 (95% CI, 2.54 to 4.76) in those with two or more minor to mild strokes, and 6.68 (95% CI, 3.77 to 11.83) in those with two or more moderate to severe strokes.
The adjusted dementia incidence rate was 0.47 (95% CI, 0.44 to 0.50) in stroke-free individuals versus 1.21 (95% CI, 1.05 to 1.40) in those with stroke.
Individuals who suffered ischemic stroke before age 75 years had a larger incremental increase in dementia risk than adults who were older at the time of stroke.
"Stroke is common, and despite decreases in stroke incidence rates over time, dementia remains a major concern for individuals with a prior stroke," Dr. Silvia Koton with Tel Aviv University in Israel and colleagues note in their paper.
"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," they point out.
"As observational data, these results do not show that treatment or prevention of stroke would reduce the risk of dementia, but they support the value of interventions aimed at reducing strokes and their severity," they say.
"Future studies should evaluate whether interventions aimed at reducing stroke severity and improving secondary prevention have an impact on dementia rates, and should monitor patients for longer durations poststroke to evaluate impact," the study team concludes.
The study had no commercial funding.
SOURCE: https://bit.ly/3H2giBX JAMA Neurology, online January 24, 2022.
By Reuters Staff
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