A recent 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 was conducted by the Michigan Medicine School. For the study, the researchers 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 which is a clot that cuts blood supply to the brain and is also the cause of over 85 per cent of all strokes, intracerebral haemorrhage which is a bleed within the brain and subarachnoid haemorrhage which is bleeding between the brain and the tissues that cover it.

The researchers 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% greater risk of intracerebral haemorrhage.

Deborah A. Levine, M.D., M.P.H., professor of internal medicine and neurology at the University of Michigan Medical School and senior author of the study said, “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 haemorrhage, especially in Black and Hispanic patients who are more likely to have uncontrolled hypertension than white patients.”

Black patients had a 20 per cent higher risk of ischemic stroke and a 67 per cent higher risk of intracerebral haemorrhage than white patients. The study also revealed that Hispanic patients had a 281% higher risk of subarachnoid haemorrhage, 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. Kimson E. Johnson, Ph.D., M.A., M.S.W., first author and postdoctoral research fellow at the University of Michigan said, “Examining racial inequities advances our understanding of the social, economic and political structures that affect health behaviours and risk for stroke among racial and ethnic minority groups.”

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.

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

She added, “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 $50 or more.

“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 optimize people's blood pressure and reduce their chances of having a stroke.”