High blood pressure has long been known to increase the risk of stroke.
But a new study from Michigan Medicine shows that it’s not just high readings in the moment that matter — it’s the long-term effects of high systolic blood pressure over many years that can significantly increase stroke risk.
Published in JAMA Network Open, the study examined data from over 40,000 adults aged 18 and older who had no history of stroke. Researchers looked at the average systolic blood pressure over time — the top number in a blood pressure reading, which measures how hard the heart pushes blood into the arteries.
The team focused on three types of stroke: ischemic stroke, which occurs when a blood clot blocks blood flow to the brain and accounts for more than 85% of all strokes; intracerebral hemorrhage, which involves bleeding within the brain; and subarachnoid hemorrhage, bleeding in the space between the brain and the tissues covering it.
Their findings were striking. People who had an average systolic blood pressure just 10 mm Hg higher than normal had a 20% higher risk of overall stroke and ischemic stroke, and a 31% greater risk of intracerebral hemorrhage.
“These results show that it’s important to detect high blood pressure early and manage it consistently throughout life to help prevent strokes,” said Dr. Deborah A. Levine, senior author of the study and professor of internal medicine and neurology at the University of Michigan Medical School.
“This is especially true for Black and Hispanic adults, who are more likely to have poorly controlled high blood pressure compared to white adults.”
The study also revealed troubling racial disparities in stroke risk. Black participants had a 20% higher risk of ischemic stroke and a 67% higher risk of intracerebral hemorrhage compared to white participants.
Hispanic participants had a 281% higher risk of subarachnoid hemorrhage than white participants, although their risks for the other stroke types were not significantly different.
Despite these differences in stroke risk, the researchers found that race and ethnicity did not appear to change the relationship between long-term systolic blood pressure and stroke type. Still, these findings shed light on the need to address broader social and healthcare issues.
“Looking at racial disparities helps us understand how social, economic, and political systems influence health and stroke risk among minority groups,” said Kimson E. Johnson, the study’s lead author and a postdoctoral fellow at the University of Michigan.
Although high blood pressure is a known risk factor for stroke and heart disease, controlling it remains a challenge. A 2020 national study found that blood pressure control in the United States actually got worse between 2013 and 2018, particularly among Black and Hispanic adults.
One way to improve blood pressure control is through home monitoring. Research shows that self-monitoring is a reliable and cost-effective way to diagnose and manage high blood pressure. However, many people don’t use home monitors, often due to lack of education or because their insurance doesn’t cover the cost of the device, which can be $50 or more.
“Doctors and health systems must educate patients about the importance of home blood pressure monitoring,” said Dr. Levine. “And insurers need to step up and cover these monitors to help people manage their blood pressure and reduce their risk of stroke.”
This study underscores the importance of lifelong blood pressure management — not just for heart health, but also to prevent life-altering or even deadly strokes.
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The study is published in JAMA Network Open.
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