Having high blood pressure may up your risk of cognitive decline, according to a new study from the National Institute of Health, which shows simply having risk factors for stroke -- not necessarily a full-blown attack -- may harm the brain.
The results, published Monday in the journal Neurology, come from the "Reasons For Geographic and Racial Differences In Stroke" or "REGARDS" study -- a multiyear effort to track stroke risk and cognitive decline among Americans age 45 and older.
Researchers found that simply having risk factors for stroke, including the number-one risk factor, high blood-pressure, and an enlarged heart, upped the risk of cognitive impairment among adults who were stroke-free and cognitively "normal."
And the more risk factors a person had, the greater his or her risk.
"There are a number of studies that back this issue of vascular health being associated with cognitive impairment," said Dr. Walter Koroshetz, deputy director of the NIH's National Institute of Neurological Disorders and Stroke, commenting on the research.
"Here, there's a conscious attempt to work with a 'normal' population, or a population that isn't really worried about their risk," he continued, explaining that the strong association found between stroke risk factors and cognitive decline among these seemingly healthy people suggests maybe they should be.
In this latest analysis, researchers tracked nearly 24,000 participants, assessing their stroke risk using the Framingham Stroke Risk Profile. It takes into account factors like age, blood pressure, diabetes, smoking habits and left ventricular hypertrophy (LVH), which is an enlargement of the heart. Researchers also tracked cognitive health annually over an average of four years.
Among people who developed cognitive impairment, age was found to be an independent risk factor, with each 10-year increment doubling the risk. LVH was also found to independently increase risk of cognitive decline by approximately 30 percent.
In a smaller, separate analysis, researchers found that high blood pressure also played a key role. Each 10 mmHG increase in systolic blood pressure -- the top number in a blood pressure reading -- was tied with an approximately 4 percent increase in risk of cognitive decline, prompting the study's authors to conclude that "hypertension may be a very important risk factor to address in order to prevent cognitive impairment."
The researchers found certain demographic risk factors for stroke, including ethnicity, were also linked to cognitive decline.
African Americans had higher risk of cognitive issues, as did people in the so-called "stroke belt," a region that includes Alabama, Arkansas, Georgia, Louisiana, Mississippi, North Carolina, South Carolina and Tennessee. Past analysis from REGARDS has put stroke mortality at about 20 percent higher in these states than elsewhere in the U.S., particularly among African Americans.
Koroshetz said scientists are not entirely sure what is driving such demographic patterns, nor do they fully understand the mechanisms underlying the association between vascular health and cognitive decline. Silent strokes and other brain abnormalities that often go unnoticed and undiagnosed may impact the brain's blood supply, putting what Koroshetz described as "wear and tear" on smaller blood vessels in the brain.
As research to better understand these issues continues, the takeaway message is one of prevention, experts say, particularly among people in their late 40s and early 50s who may not necessarily realize they are at risk. People should work with their health care providers to make sure they are tracking and managing the various elements of vascular health.
"The message for reader is, you may think you are 'normal,'" Koroshetz said. "But make sure that you have these risk factors under control."