If your systolic blood pressure (the top number in your blood pressure) is consistently higher than normal, a new study from the University of Michigan suggests you are at increased risk of stroke.
A study published in JAMA Open Network found that if a person’s systolic blood pressure is 10 points above the 120 mmHg threshold for a prolonged period, the risk of ischemic stroke is 20% higher and the risk of intracerebral hemorrhage increases by 31%.
“We focused on systolic blood pressure because it is the best predictor of cardiovascular outcomes, particularly stroke but also heart attack,” said Dr. Deborah Levine, professor of medicine at the University of Michigan Medical School and lead author of the study, which analyzed data from more than 38,000 U.S. adults over an average period of 21 years.
“We combined six studies that followed participants for many years and recruited participants at different ages to examine how high blood pressure over the life course influences stroke risk.”
According to the Michigan Department of Health and Human Services, stroke is the fifth leading cause of death in Michigan, killing 5,775 people in 2022 alone. More than a third of Michigan adults have high blood pressure.
“High blood pressure is underdiagnosed, undertreated and undercontrolled,” Levine said. “And yet it is the single most important risk factor for stroke.”
The research, Levine said, underscores the importance of identifying high blood pressure early and taking steps to reduce it, such as adopting better eating and exercise habits and adding blood pressure medications when lifestyle changes alone aren’t enough.
“Health care providers need to intensify blood pressure treatment, to maintain blood pressure at target levels in all adults,” she said.
Racial disparities in stroke prevalence
The study looked at data from a diverse group of patients: 54% were women; 25% were black; 8.9% identified as Hispanic; and 66.2% identified as white.
The researchers found no racial or ethnic differences in stroke risk associated with long-term high systolic blood pressure, although black and Hispanic Americans are disproportionately affected by stroke.
“We did not find evidence that higher cumulative systolic blood pressure has a greater effect on stroke risk in black or Hispanic adults than in white adults,” Levine said. “So this suggests that … higher blood pressure in these minority groups is likely due to poorer access to care, treatment, and blood pressure control.”
Blood pressure control makes a difference
“Adults should monitor their blood pressure at home regularly to ensure it is at the desired level. Visiting your doctor once a year is just a snapshot. In parallel, my group has shown how home monitoring improves blood pressure diagnosis and control and is an underutilized but highly effective and cost-effective strategy.”
Because blood pressure readings can be affected by outside factors such as stress, anxiety, caffeine and alcohol consumption, Levine recommends that all adults 30 and older measure their blood pressure at home twice a day for one week each month. An average of that week’s readings will give a better idea of your actual blood pressure.
Taking measurements at home can also eliminate what’s known as the “white coat effect,” which occurs when a person’s blood pressure rises while in a doctor’s office because they’re nervous or anxious about the appointment.
Home blood pressure monitors can be purchased for as little as $20 to $25. Levine recommends purchasing a monitor that has been tested by the independent U.S. Blood Pressure Validated Device Listing website, www.validatebp.org, and provides accurate readings.
“Unfortunately, most insurance companies don’t cover them,” Levine said. While paying $20 to $25 for a home monitor isn’t out of reach for some people, others can’t afford the expense, exacerbating health inequities.
“Although self-monitoring of blood pressure improves blood pressure control and is cost-effective, it is an underutilized tool and cost is a barrier, making patient education and greater insurance coverage priorities,” the study authors wrote.
What is considered high blood pressure?
“High blood pressure is defined as blood pressure of 130/80 or higher on at least two occasions,” Levine said.
The top number, systolic blood pressure, measures the pressure on the artery walls with each heartbeat. Diastolic pressure is the bottom number in a measurement and measures the pressure on the artery walls when the heart rests between beats.
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Until 2017, the threshold for classifying hypertension was set at 140/90 mmHg. But research published at that time led the American Heart Association, the American College of Cardiology, and other health organizations to lower the definition of hypertension to 130/80 mmHg.
According to the new guidelines, blood pressure levels should be calculated by averaging two to three measurements taken on at least two separate occasions.
- Normal is considered to be less than 120/80 mmHg.
- High blood pressure occurs when a person has a systolic pressure of 120 to 129 mmHg (top number) and a diastolic pressure (bottom number) less than 80 mmHg.
- Stage 1 hypertension is classified as a systolic blood pressure between 130 and 139 mmHg or a diastolic blood pressure between 80 and 89 mmHg.
- Stage 2 hypertension occurs when the systolic pressure is at least 140 mmHg or the diastolic pressure is at least 90 mmHg.
- A hypertensive crisis is a medical emergency and occurs when the systolic pressure is greater than 180 mmHg and/or the diastolic pressure is greater than 120 mmHg.
Many people are unaware of the now lower thresholds for what should be considered high blood pressure, Levine said. Others have heard inaccurate information about high blood pressure.
“When I see patients who have recently had a stroke, I’m really sad to see that many of them had high blood pressure before the stroke and it wasn’t managed,” Levine said.
“Another myth is that older people are allowed to have higher blood pressure, that they don’t need to control it. But that’s not true. We need to treat all adults the same, regardless of age.”
Recipe to reduce blood pressure
When it comes to high blood pressure, sometimes the best cure is lifestyle changes, Levine said.
Levine recommends:
- A low-salt diet, consuming less than 1,500 milligrams of salt per day.
- Exercise for 30 minutes, five days a week.
- Weight loss for anyone who is overweight or obese based on body mass index.
- Avoid or limit alcohol consumption.
- Talk to your doctor about whether you also need medication to control your blood pressure.
Contact Kristen Shamus: kshamus@freepress.com. Subscribe to the Free Press.