High Blood Pressure May Be Linked to Alzheimer’s Disease
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Researchers say hypertension in older adults can cause tangles and plaques to form in the brain. Both are common markers of Alzheimer’s disease. It’s well-documented that high blood pressure increases the risk of heart disease.
Now, new research suggests that hypertension can also seriously affect your brain — perhaps to the point of developing some of the primary markers of Alzheimer’s disease.
High blood pressure occurs when the force of blood pushing against the inside of our blood vessels is too high. High blood pressure causes harm by stressing the heart and blood vessels. They have to work harder, and they become less efficient.
According to the Mayo Clinic, over time this stress damages the delicate tissues inside your arteries. Eventually, low-density lipoprotein (LDL) cholesterol, sometimes called bad cholesterol, collects along tiny tears in the artery walls. This causes the arteries to narrow, a condition called atherosclerosis. This increases blood pressure.
As this damage increases, the arteries become narrower. This raises blood pressure even further, starting a process that can lead to problems ranging from irregular heartbeat to heart attack to stroke.
New research recently published in the journal Neurology now indicates that older people with higher average blood pressure compared to their peers are also more likely to develop tangles and plaques in their brain. Both are markers of Alzheimer’s disease.
What the study showed
The study included 1,288 participants age 65 or older. About two-thirds were women. The participants received annual blood pressure checks and cognitive testing. Researchers also kept track of the participants’ medical histories and the medications they took.
Participants were required to allow a brain autopsy after death to look for signs of brain aging, such as tangles and plaques. Researchers found that people who had higher than average blood pressure showed more dead brain tissue caused by strokes (blocked blood flow) as well as plaques and tangles.
“Tangles and plaques can happen when proteins that are normally produced in the body, break down to toxic forms that affect neurons in the brain,” explained Dr. Claudia Padilla, a neurologist affiliated with Baylor University Medical Center and an assistant professor of neurology at Texas A&M College of Medicine.
James Hendrix, PhD, director of global science initiatives at the Alzheimer's Association, notes that the damage caused by toxic proteins is only part of the problem. “A lack of proper blood flow to the brain can make the brain less able to work around damaged tissue,” Hendrix told Healthline. He says this can make any symptoms of brain tissue damage significantly worse.
Not necessarily proof
Padilla notes that because this recent research was an observational study, the findings don’t actually prove that high blood pressure caused the signs of Alzheimer’s disease.
“How higher average late-life blood pressure may increase tangles and plaques in the brain wasn’t determined by this study,” she said.
However, Padilla agrees that “This study did find a clear association between higher blood pressure in later life and the presence of protein tangles and plaques symptomatic of Alzheimer’s.”
Hendrix says it’s important to recognize the relationship between high blood pressure and cognitive functioning. “While this study doesn’t prove that hypertension causes Alzheimer’s, it will increase the risk of vascular dementia, which impacts cognitive ability in large numbers of people.”
Regardless, Padilla considers controlling blood pressure an important strategy to prevent cognitive decline.
“Recent research suggests that hypertension in midlife can increase the risk of dementia, specifically vascular dementia, if high blood pressure is not well-controlled with antihypertensive medications,” she said.
Higher pressure, more damage
The study participants had an average systolic blood pressure (the pressure when the heart beats) of 134 and an average diastolic blood pressure (the pressure when the heart relaxes) of 71.
However, over half had a history of high blood pressure and roughly 90 percent of them had been prescribed drugs for hypertension. Researchers found that as systolic blood pressure rises, so does the risk of tissue damage. For example, having a systolic reading of 147 was found to increase the risk of developing brain lesions by 46 percent.
Hendrix says that this type of damage can “seriously impact brain function.”
“Brain lesions, caused by stroke or other factors, may significantly affect memory, thinking, and behavior. Many people can develop depression and anxiety,” said Padilla.
High blood pressure can cause an array of serious health problems, but there are things you can do to reduce your risk.
For people already living with hypertension, “Previous studies have already shown that patients on blood pressure medication had less cognitive decline than untreated individuals with hypertension,” says Padilla.
For everyone else, Padilla recommends “exercise, maintaining a healthy weight, cutting back on salt, and not smoking” as some of the lifestyle approaches that will help keep your blood pressure in a healthy range.
According to Hendrix, people should keep in mind that “what’s good for the heart is good for the brain.” However, Hendrix cautions that the current blood pressure recommendations are intended for people in middle age.
He says lower blood pressure in older adults can cause other issues. “Low blood pressure can cause dizziness, leading to falls or other accidents,” he says.
Hendrix concludes, “What we really need is more specific research on blood pressure in older populations.”