Some 46% of the 1.28 billion adults around the world with high blood pressure don’t know they have it, according to the World Health Organization. Yet living with uncontrolled hypertension may dramatically raise the risk of Alzheimer’s disease for people ages 60 and older, according to a new metanalysis.

People with untreated high blood pressure had a 36% higher risk of Alzheimer’s disease when compared with people without high blood pressure, and a 42% increased risk of Alzheimer’s when compared with people who were taking blood pressure medications to control their hypertension, according to the analysis.

“This relationship is not altered by increasing age, which indicates that even those in their 70s and 80s are at significantly lower risk of Alzheimer’s disease if hypertension is treated,” said senior author Dr. Matthew Lennon, a researcher at the Centre for Healthy Brain Ageing at the University of New South Wales in Australia, in an email.

In addition, people with unmedicated hypertension had a 69% greater risk of other non-Alzheimer’s types of dementia compared with those without hypertension, while those with poorly controlled, medicated hypertension had 33% increased risk, Lennon said.

If the blood pressure was controlled by medication, however, there was no elevated risk of non-Alzheimer’s dementia, such as vascular, frontotemporal and Lewy body dementia, he said.

Unfortunately, many people with diagnosed high blood pressure fail to take their medications on a regular basis or have treatment-resistant hypertension. In fact, only about 1 in 5 adults have their condition under control, according to WHO.

“The stats on blood pressure are scary,” said Dr. Andrew Freeman, director of cardiovascular prevention and wellness at National Jewish Health in Denver. He was not involved in the new study.

“For every 20 points on average that somebody goes above 120 systolic (the top number of a blood pressure reading) the risk for a cardiovascular event doubles,” he said. “It’s a superpotent risk factor that most people don’t pay enough attention to or properly manage.”

Yet if people think of blood pressure as only affecting their heart, a huge part of the story is missing, Freeman said.

“If you have a coronary event, it’s your entire body that’s affected,” he said. “You have blood vessel disease that can occur anywhere in the body, including in the brain and the periphery.”

In fact, uncontrolled high blood pressure has long been linked to a much higher risk for kidney disease, stroke, type 2 diabetes and overall dementia as well as heart disease, said preventive neurologist Dr. Richard Isaacson, director of research at the Institute for Neurodegenerative Diseases in Boca Raton, Florida.

While the development of beta-amyloid clusters and an explosion of tau tangles is thought to drive Alzheimer’s disease, unchecked drivers of chronic diseases fan the flame of inflammation in the brain, said Isaacson, who was not involved in the new study.

“Uncontrolled vascular risk factors like high blood pressure, high cholesterol and diabetes are not necessarily going to cause Alzheimer’s disease, but they will fast-forward Alzheimer’s pathology and increase risk,” Isaacson said.

A global view of blood pressure and dementia

The metanalysis, published Wednesday in the journal Neurology, analyzed four years of data on over 31,000 people with an average age of 72 from 14 countries: Australia, Brazil, China, France, Germany, Greece, Italy, Japan, Korea, Nigeria, the Republic of Congo, Spain, Sweden and the United States.

The study did not find any significant differences among sexes or racial groups when it came to blood pressure control and an increased risk for Alzheimer’s.

“This is a very promising result as it suggests that optimal care for one group will be similar for others,” Lennon said. “It is critical that an understanding of chronic illness management in the developing world is published and disseminated. It is precisely in these areas where chronic illnesses are least well understood but is also where the majority of new dementia cases will occur in the coming decades.”

People with untreated high blood pressure had a 110% higher risk of vascular dementia — the second most common form of dementia after Alzheimer’s disease — compared with people without hypertension, and a 71% higher risk when compared with people with treated high blood pressure, Lennon said. But due to the small sample size, those results failed to reach statistical significance when the studies were fully adjusted for confounding factors, he said.

However, scientific literature is packed with studies that show hypertension damages small blood vessels and reduces blood flow to the brain. It’s possible the studies in this new metanalysis may not have followed people long enough to show an association, Lennon said.

The metanalysis did show a U-shaped association between Alzheimer’s and high blood pressure that was dependent on age, which makes a one-size-fits-all approach to treating the condition difficult, Isaacson said.

“The challenge with choosing blood pressure targets for optimal dementia or Alzheimer’s prevention lies in this U-shaped curve: If blood pressure is too low that may potentially increase risk, and if blood pressure is too high, that also increases risk,” he said.

“The general blood pressure targets we advocate for when it comes to systolic, the top number, are low 120s or below, and low 70s or below for the diastolic, or bottom number,” Isaacson said. “However, each person should check with their doctor and have those numbers personalized.”

How to take charge of your blood pressure

You can protect yourself from accelerating your risk for Alzheimer’s and other chronic diseases associated with uncontrolled hypertension, according to experts.

Track your numbers: Because blood pressure fluctuates widely throughout the day, taking a one-time baseline reading doesn’t work, experts say. Instead, taking multiple readings a day over several days is needed to accurately know one’s true blood pressure numbers, Freeman said.

Try to take those readings at the same time each day to accurately capture how your blood pressure trends, the American Heart Association recommends on its website.

Choose a certified blood pressure cuff: The AHA recommends choosing a validated, automatic, cuff-style, upper-arm monitor. Don’t choose a wrist or finger monitor as they are not as reliable.

“Choose a monitor that has been validated. If you are unsure, ask your health care professional or pharmacist for advice or find options at validatebp.org,” the AHA says.

Picking one with a memory card that tracks numbers is helpful; otherwise, have a dedicated journal to record your readings.

Do it right: Don’t smoke, drink caffeinated beverages or exercise for at least 30 minutes before measuring your blood pressure, the AHA says. Go to the bathroom and empty your bladder.

Sit with your back straight and supported, which means sitting on a hard-backed chair at a desk or table, not a sofa. Sit quietly for a few minutes with your feet flat on the floor — no crossed legs — and keep the arm being tested at heart level supported by a horizontal surface such as a table.

Take your pressure in both arms on regular occasions — studies have shown that a difference in readings between two arms may be a warning sign of a future heart attack or stroke.

Take your blood pressure meds daily: One of the biggest mistakes people make when it comes to properly controlling hypertension is a failure to take their medications on a daily basis, experts say.

“These drugs are not like cholesterol drugs, which may last in your system for a day or so,” Isaacson said. “Many of them have very short half-lives so taking them as prescribed is absolutely critical.”

Don’t rely on your memory when it comes to critical medications. Instead, use a tracking device, such as a pill holder marked with days of the week, that’s filled in advance. Then, if you skip a dose, it will be readily apparent.

“If I say to a patient, are you taking your drugs, they always say yes,” Freeman said. “But if I ask them, ‘Hey, over the last week, how many times do you think you may have missed the dose?’ It’s usually more than zero.

“High blood pressure doesn’t tend to regress or go away, unless people make significant lifestyle changes or take their drugs or both,” he added.

Consider lifestyle changes: Diets that stress lower sodium intake and plenty of fruits, vegetables, whole grains and good fats really work, experts say. The award-winning DASH diet, which stands for Dietary Approaches to Stop Hypertension, is an expert-approved method of lowering salt intake to 2,300 milligrams a day, the top daily limit for people age 14 and older recommended by the latest US nutritional guidelines. 

However, the AHA recommends a diet with less than 1,500 milligrams of sodium a day.

In fact, cutting 2,300 milligrams, which is about 1 teaspoon of salt, from your diet each day for a week can lower your top blood pressure reading just as much as a typical hypertension medication, according to a November 2023 study.

“It turns out that when we get that potassium and other nutrients from the fruits and vegetables in our system, it tends to lower blood pressure quite dramatically,” Freeman said.

However, one of the most potent anti-high blood pressure treatments that ever existed is regular exercise, experts say.

“Obviously people should check with their doctors, but 30 minutes of brisk, breathless exercise a day is an amazing way to control blood pressure,” Freeman said. “Combine that with diet, stress relief and good-quality sleep, and people usually end up with surprisingly well-controlled blood pressure, with not nearly as much or any medication.”