The study found that people with high diastolic blood pressure, which is the bottom number of a blood pressure reading, were more likely to have cognitive impairment, or problems with their memory and thinking skills, than people with normal diastolic readings.
For every 10 point increase in the reading, the odds of a person having cognitive problems was seven percent higher. The results were valid after adjusting for other factors that could affect cognitive abilities, such as age, smoking status, exercise level, education, diabetes or high cholesterol.
The study involved nearly 20,000 people age 45 and older across the country who participated in the Reasons for Geographic And Racial Differences in Stroke (REGARDS) Study and had never had a stroke or mini-stroke. A total of 1,505 of the participants, or 7.6 percent, had cognitive problems, and 9,844, or 49.6 percent, were taking medication for high blood pressure.
High blood pressure is defined as a reading equal to or higher than 140/90 or taking medication for high blood pressure.
"It's possible that by preventing or treating high blood pressure, we could potentially prevent cognitive impairment, which can be a precursor to dementia," said study author Georgios Tsivgoulis, MD, of the University of Alabama at Birmingham and a member of the American Academy of Neurology.
Research has shown that high diastolic blood pressure leads to weakening of small arteries in the brain, which can result in the development of small areas of brain damage.
Tsivgoulis said more research is needed to confirm the relationship between high blood pressure and cognitive impairment.
The study was supported by the National Institute of Neurological Disorders and Stroke (NINDS).
"The REGARDS study is one of the largest population-based studies of risk factors for stroke. These latest data suggest that higher blood pressure may be a risk factor for cognitive decline, but further studies will be necessary to understand the cause-effect relationship," said Walter J. Koroshetz, MD, deputy director of NINDS and Fellow of the American Academy of Neurology. "The National Institutes of Health is now organizing a large clinical trial to evaluate whether aggressive blood pressure lowering can decrease a number of important health outcomes including cognitive decline."