High blood pressure may increase risk of strokes

A Michigan Medicine study found that high systolic blood pressure (the top number on the blood pressure reading and how hard the heart pumps blood to the arteries) increases the risk of the two most common types of strokes over time.

The study looked at the average systolic blood pressure years before the first stroke in over 40,000 adults aged 18 and older who had no history of stroke.

Researchers covered three types of stroke: ischemic, a clot that cuts blood supply to the brain and the cause of over 85 per cent of all strokes; intracerebral hemorrhage, a bleed within the brain; and subarachnoid hemorrhage, bleeding between the brain and the tissues that cover it.

They found that having a mean systolic blood pressure that is 10-mm Hg higher than average was associated with a 20 per cent higher risk of overall stroke and ischemic stroke, as well as a 31 per cent greater risk of intracerebral hemorrhage.

"Our results suggest that early diagnosis and sustained control of high blood pressure over the lifespan are critical to preventing stroke, ischemic stroke and intracerebral hemorrhage, especially in Black and Hispanic patients who are more likely to have uncontrolled hypertension than white patients," said senior author Deborah A Levine, professor of internal medicine and neurology at University of Michigan Medical School.

Black patients had a 20 per cent higher risk of ischemic stroke and a 67 per cent higher risk of intracerebral hemorrhage than white patients.

Hispanic patients had a 281 per cent higher risk of subarachnoid hemorrhage, but not any other stroke type, compared to white patients.

While Black and Hispanic patients had a higher risk of stroke, researchers found little evidence to suggest that race and ethnicity affected the association between cumulative systolic blood pressure and the type of stroke that affected any patient.

"Examining racial inequities advances our understanding of the social, economic and political structures that affect health behaviors and risk for stroke among racial and ethnic minority groups," said Kimson E Johnson, first author and postdoctoral research fellow at the University of Michigan.

While systolic blood pressure is a modifiable target for preventing stroke and other cardiovascular diseases, a national study conducted in 2020 found that blood pressure control in the United States worsened from 2013 to 2018, especially for Black and Hispanic adults.

Self-monitoring of blood pressure improves blood pressure diagnosis and control and is accurate and cost-effective, but it remains an underused tool, Levine says.

"Two major barriers to self-monitoring of blood pressure are lack of patient education and insurance not covering the home blood pressure monitors, which cost USD 50 or more," she said.

"Health care systems and providers must educate and urge their patients to do home blood pressure monitoring, and insurers must pay for home blood pressure monitors to optimise people's blood pressure and reduce their chances of having a stroke."