Lowering blood pressure may help prevent dementia
High blood pressure can damage the brain in several ways. Treating this common problem can protect your mind as well as your heart.
High blood pressure seldom causes any symptoms. But over time, the excessive force and friction of blood pushing against the inner walls of the arteries can damage blood vessels throughout the body. And while the biggest threat may be to your heart, your brain can also suffer.
Even slightly elevated blood pressure in middle age has been linked to a 30% higher risk of dementia two decades later. But taking blood pressure drugs may help people avoid that risk, according to a study in the May 19, 2020, issue of JAMA.
The study included findings from 12 studies involving more than 92,000 people. Their average systolic blood pressure (the first number in a blood pressure reading) was 154 mm Hg; their average diastolic reading (the second number) was 83 mm Hg. After a follow-up period (about four years on average), the risk of dementia or cognitive impairment was about 7% lower among people who took blood pressure drugs compared with those who didn't.
"This study underscores the thinking that lowering blood pressure is likely to be an effective way to prevent cognitive impairment," says Dr. Steven Greenberg, professor of neurology at Harvard Medical School. People with cognitive impairment struggle to remember and learn new things and have trouble with concentration and decision making. The condition is often a forerunner to dementia, which refers to more serious memory and thinking problems that affect everyday living.
High blood pressure's harms
High blood pressure can damage both the large and small blood vessels of the brain, probably in slightly different ways, explains Dr. Greenberg. High blood pressure accelerates the process of atherosclerosis, the buildup of fatty plaque inside artery walls, which leaves you prone to an ischemic stroke. These strokes occur when a blood clot blocks an artery in the brain. If an ischemic stroke affects an area of the brain important for cognition, it can contribute to a condition called vascular dementia. But increasingly, evidence suggests that vascular dementia often stems from damage to the brain's smaller vessels.
High blood pressure causes the walls of the smaller arteries in the brain to thicken, setting the stage not just for ischemic strokes, but also hemorrhagic strokes. Also called bleeding strokes, hemorrhagic strokes happen when a brain blood vessel leaks or ruptures.
Minor strokes stemming from damage to these smaller vessels may go unnoticed. But if people experience many small, "silent" strokes, the damage can accumulate, leading to problems with thinking.
The damage is visible on MRI scans as bright spots called white matter lesions (white matter consists of bundles of nerve fibers that connect brain cells). Nearly everyone over age 60 has these lesions, which may contribute to normal, age-related memory loss. But people with high blood pressure have more extensive white matter damage.
An evolving view of dementia
Our understanding of dementia has evolved over the past decade. Experts now recognize that many people who lose their memory with age have more than one type of dementia, including Alzheimer's disease, vascular dementia, and other, less common forms. "While we're still waiting for a breakthrough for Alzheimer's prevention, it's good to know we have common medications at hand that can help prevent dementia," says Dr. Greenberg. The fact that the study showed measurable benefits from taking blood pressure drugs over just four years is especially encouraging, he adds.
What's more, the results line up with findings from a 2016 study in The New England Journal of Medicine showing that the age-adjusted rates of dementia have been slowly dropping over time. The disease is also showing up later in life: the average age of a dementia diagnosis went from 80 to 85 over the past 30 years. One possible explanation: the increased focus on treating high blood pressure and other heart-related risks that occurred over that same time period, says Dr. Greenberg. Bottom line: If your blood pressure is higher than normal (see "Blood pressure categories"), treatment will likely benefit your brain as well as your heart.
Blood pressure categories |
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Blood pressure category |
SYSTOLIC |
|
DIASTOLIC |
|
Normal |
Less than 120 mm Hg |
and |
Less than 80 mm Hg |
|
Elevated |
120–129 mm Hg |
and |
Less than 80 mm Hg |
|
High blood pressure: |
130–139 mm Hg |
or |
80–89 mm Hg |
|
High blood pressure: |
140 mm Hg or higher |
or |
90 mm Hg or higher |
|
Hypertensive crisis (consult your doctor immediately) |
Higher than 180 mm Hg |
and/or |
Higher than 120 mm Hg |
|
Source: American Heart Association and American Stroke Association. |
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Image: © Nik01ay/Getty Images
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