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Stroke risk – even without a stroke – may indicate future cognitive decline

Nov. 7, 2011

By Patricia Nicholson

Risk factors for stroke may also predict risk of future cognitive problems, even in people who never have a stroke.

A new study involved 23,752 people with no history of stroke and no cognitive problems at the start of the study. The results showed that those with the highest stroke risks also had the highest rates of cognitive decline over the next few years.

Researchers at the Indiana University School of Medicine measured both stroke risk and cognitive function in people ages 45 or older (average age 64). They followed the group for four years, measuring cognitive function once a year and monitoring for stroke. For participants who had a stroke during the course of the study (196 people), only test results prior to the stroke were included in the research results. The other 23,556 participants were stroke-free throughout the study.

About eight per cent of the study group (1,907 people) experienced cognitive decline during the course of the study. Cognitive function was measured using a six-item screening test. A score of four or less out of six indicates impaired cognitive function. People who developed cognitive problems during the study were those whose score dropped from five or six at the start of the study, to four or less during followup.

Stroke risk was determined using the Framingham Stroke Risk Profile (FSRP), which uses factors such as age, blood pressure, history of cardiovascular disease, diabetes, smoking and left ventricular hypertrophy, or LVH (thickening of the muscle wall of the heart’s pumping chamber).

The participants were divided into four groups based on their stroke risk scores. Among those with the highest stroke risk scores, almost 15 per cent developed cognitive problems over the followup period, compared to about three per cent among people with the lowest stroke risk scores.

The average FSRP score among people who developed cognitive problems was 15.2, compared to 9.1 in people who did not experience cognitive decline.

Two individual stroke risk factors, in addition to total FSRP score, were linked to cognitive decline: LVH and older age. LVH increased risk of cognitive problems by 29 per cent, and risk doubled with each additional 10 years in age.

Because high blood pressure is a common cause of LVH, the researchers did a second analysis that did not include people with LVH. This second analysis found that among people who don’t have LVH, high systolic blood pressure was also a risk factor for cognitive decline. Each 10 mm Hg increase in systolic blood pressure (the top number of the blood pressure reading) increased the risk of cognitive problems by four per cent.

Stroke risk and cognitive risk may be linked because of several underlying brain factors that are associated with both conditions, but that cause no immediate symptoms. These include abnormalities in the brain’s white matter, and silent cerebral infarctions (tiny strokes that are so small they go unnoticed, but that can damage the brain).

The study results suggest that high risk of stroke, as well as some individual stroke risks, may predict risk of future cognitive problems, even in people who never have a stroke.

The study appears in the Nov. 8, 2011 issue of Neurology.

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  • Women's College Hospital