Number and Severity of Strokes Increase Risk for Dementia

The findings emphasize the need to come up with dementia prevention protocols,  not your stroke prevention idea. Solve the problem directly, not indirectly. It will be useful in many more instances.

Number and Severity of Strokes Increase Risk for Dementia

By Mary Beth Nierengarten

March 3, 2022

Article In Brief

A large community-based cohort study found that adults who had one stroke were nearly twice as likely to have dementia as individuals who did not have a stroke. In addition, the risk for developing dementia was nearly seven times higher in those who had two or more moderate to severe strokes. The findings emphasize the value of both primary and secondary stroke prevention for reducing dementia risk and for achieving high levels of function and quality of life, especially at older ages.

Adults who had one stroke were nearly twice as likely to have dementia as individuals who did not have a stroke, and the risk for developing dementia was nearly seven times higher in those who had two or more moderate to severe strokes, according to a large community-based cohort study published online on January 24 in JAMA Neurology.

The study built on prior data suggesting that the risk of dementia increases with the severity and number of strokes.

The study provides more detailed and comprehensive data on risk factors for stroke and dementia, and that allowed the investigators to uniquely characterize the link between the two, said the lead author Silvia Koton, PhD, a stroke epidemiologist and head of the Herczeg Institute on Aging at Tel Aviv University.

“The strength of the association between stroke occurrence, stroke severity, and risk of dementia is impressive,” Dr. Koton said, adding that the findings suggest a dose-response association in which the risk of dementia increases for every additional stroke after the first stroke. The study also found that the risk of dementia following stroke increased after adjusting for vascular risk factors.

“Our findings emphasize the value of both primary and secondary stroke prevention for reducing dementia risk and [for] achieving high levels of function and quality of life, especially at older ages,” said Dr, Koton.

Study Details

In the study, Dr. Koton and colleagues examined the associations between dementia and ischemic stroke incidence, frequency, and severity in 15,379 participants enrolled in the Atherosclerosis Risk in Communities (ARIC) study, an ongoing prospective cohort of community-dwelling persons in four US states conducted to better understand the impact of atherosclerosis on clinical outcomes.

The participants included in the study did not have a history of stroke and dementia at baseline in 1987 to 1989 and were monitored through 2019 via an average of 4.4 visits and follow-up phone calls conducted yearly until 2021 and every six months since 2012. Most of the participants were White (73.3 percent), the mean age of the participants was 54.1 years, and just over half (55.2 percent) were women.

“Our findings emphasize the value of both primary and secondary stroke prevention for reducing dementia risk and [for] achieving high levels of function and quality of life, especially at older ages.”—DR. SILVIA KOTON

Over a median follow-up of 25.5 years, a total of 1,378 ischemic strokes—1,155 incident events—occurred as did 2,860 cases of dementia (dementia occurring in the first year after stroke was not included). Scores on the National Institutes of Health Stroke Scale (NIHSS) indicated that 62.8 percent of 1,184 strokes were minor, 21.1 percent were mild, 7.9 percent were moderate, and 7.1 percent were severe.

The proportion of dementia risk attributed to stroke was 17.4 percent and increased with the frequency of stroke from 9.1 percent for one stroke to 53 percent for more than two strokes, as well as by severity of stroke from 7 percent for minor stroke to 50 percent for severe stroke.

After adjusting for demographic and vascular risk factors, the study found increased hazard rates of dementia associated with stroke frequency and severity. Compared with no stroke, the risk of dementia was 1.73 times higher for one minor to mild stroke, nearly 3.5 times higher for one moderate to severe stroke, nearly 3.5 times higher for two or more minor to mild strokes, and nearly seven times higher for two or more moderate to severe strokes.