Years of high blood pressure show ‘clear link’ to higher stroke risk

High blood pressure has long been known as a major risk factor for stroke, but new research from Michigan Medicine reveals just how insidious this “silent killer” can be over time. The study sheds light on the cumulative effects of elevated systolic blood pressure throughout adulthood, showing a clear link to increased risk for the most common and dangerous types of stroke.

The research team, led by Dr. Deborah A. Levine, analyzed data from over 40,000 adults aged 18 and older who had no prior history of stroke. They focused on systolic blood pressure – the top number in a blood pressure reading, which indicates how much pressure your blood is exerting against your artery walls when your heart beats.

The findings are striking: for every 10 mm Hg increase in a person’s long-term average systolic blood pressure, their risk of stroke overall increased by 20%. This same 20% increase applied specifically to ischemic strokes, which occur when a blood clot blocks blood flow to the brain and account for about 85% of all strokes. Even more alarming, the risk of intracerebral hemorrhage – bleeding within the brain tissue – jumped by 31% for each 10 mm Hg increase.

“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,” says Dr. Levine, a professor of internal medicine and neurology at the University of Michigan Medical School, in a statement.

The study, published in JAMA Network Open, also revealed significant racial and ethnic disparities in stroke risk. Compared to white patients:

• Black patients had a 20% higher risk of ischemic stroke and a 67% higher risk of intracerebral hemorrhage.
• Hispanic patients had a startling 281% higher risk of subarachnoid hemorrhage (bleeding in the space surrounding the brain), though their risk for other stroke types was not significantly different.

Interestingly, while these baseline differences in risk exist, the researchers found little evidence to suggest that race and ethnicity affected how strongly cumulative blood pressure influenced stroke risk. In other words, the dangers of sustained high blood pressure appear to be relatively consistent across racial and ethnic groups.

“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,” says lead author Dr. Kimson E. Johnson, a postdoctoral research fellow at the University of Michigan.

This research comes at a critical time. Despite decades of public health efforts, a national study in 2020 found that blood pressure control in the United States actually worsened between 2013 and 2018, with Black and Hispanic adults facing the steepest declines.

The good news is that blood pressure is a modifiable risk factor. Lifestyle changes like regular exercise, a healthy diet low in sodium, maintaining a healthy weight, limiting alcohol intake, and not smoking can all help lower blood pressure. For those who need additional support, there are many effective medications available.

However, a key challenge remains: many people are unaware they have high blood pressure or struggle to monitor it effectively. Dr. Levine points out that while self-monitoring of blood pressure is accurate and cost-effective, it remains underutilized.

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

This study serves as a wake-up call for both individuals and the healthcare system. By understanding the long-term risks of elevated blood pressure and addressing the barriers to effective monitoring and control, we have the potential to significantly reduce the burden of stroke across all communities.