Most people know that high blood pressure can damage the heart, but it can also affect the brain.
Research from the University of Miami suggests that the lower number in a blood pressure reading may provide useful information about a person’s risk of small areas of brain damage linked to stroke and memory problems.
The study was led by Michelle R. Caunca and published in the journal Stroke. Researchers examined 1,205 adults aged 50 and older and compared their blood pressure readings with detailed MRI scans of their brains.
A blood pressure reading contains two numbers. The upper number, called systolic pressure, measures the force against artery walls when the heart contracts and pushes blood around the body.
The lower number is called diastolic pressure. It measures the pressure in the arteries while the heart relaxes between beats and fills with blood again.
Doctors often pay particular attention to systolic pressure because it is strongly linked to heart disease and stroke, especially as people get older. However, the new findings suggest that diastolic pressure may also provide important clues about the health of small blood vessels in the brain.
The researchers looked for changes known as white matter lesions, which appear as damaged areas on brain scans. White matter contains millions of nerve fibers that allow different areas of the brain to send information to one another.
When this tissue is damaged, communication between brain regions can become less efficient. Greater amounts of white matter damage have been associated with problems involving memory, thinking, walking, balance, falls, and a higher risk of stroke.
In the study, people whose diastolic blood pressure was below 80 had fewer white matter lesions than people whose diastolic pressure was above 90. The relationship was especially noticeable for lesions located around fluid-filled spaces in the brain called the ventricles.
These areas are known as periventricular white matter. Damage there has attracted attention because it has been associated with cognitive decline and other changes in brain function as people age.
White matter lesions become increasingly common with age. According to information cited from the American Heart Association, they can already be found in some people by around age 60 and become extremely common among very old adults.
High blood pressure can damage the small arteries that supply the brain. Over many years, artery walls may become thicker or less flexible, reducing the steady flow of oxygen and nutrients that brain tissue needs.
Earlier research has strongly connected high systolic blood pressure with this type of small-vessel damage. The University of Miami study adds evidence that diastolic pressure may also be important, and that the two blood pressure numbers can provide different information about brain health.
However, the findings do not mean that people should try to lower their diastolic blood pressure as much as possible. Blood pressure that becomes too low can also cause problems, and the healthiest target depends on factors such as age, medical conditions, medications, and overall cardiovascular health.
The study also shows an association rather than proving that a particular diastolic pressure directly causes or prevents brain lesions. More research is needed to understand exactly how blood pressure affects different areas of the brain over time.
Still, the findings offer another reason to know both numbers in a blood pressure reading. Regular monitoring and appropriate treatment of high blood pressure may help protect not only the heart and arteries but also the brain as people grow older.
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