• A large meta-study finds that older people whose hypertension is under control have no greater risk of dementia than a person without hypertension.
• However, people with uncontrolled hypertension are at a higher risk of dementia.
• The study hopes to clarify the relationship between hypertension and dementia.

It is known that hypertension, or high blood pressure, is linked to dementia, but in what way has been unclear.

Now, an expansive new meta-study finds that older people who continue to take antihypertensive medications have a 26% lower risk of all-cause dementia than people with untreated hypertension.

Hypertension is the greatest risk factor for dementia, affecting well over one billion people worldwide. Hypertension in midlife has been linked in some studies to a roughly 60% increase in the risk of all-cause dementia later on — and about a 25% greater chance of Alzheimer-related dementia.

The new study is a meta-study, or study of studies, involving 17 different investigations. It is unusual for its size and scope and significant for its inclusion of 34,519 community-dwelling older adults from 15 different countries located in Asia, Africa, Europe, Australia, and North and South America.

The participants’ mean age was 72.5, and 58.4% of them were female. From that group, 14,759 individuals — about half — had treated hypertension, while 2,881 participants had hypertension that was not treated. There were 10,402 individuals who served as healthy controls. All were dementia-free at the start of the study and were followed for an average of 4.3 years.

The researchers confirmed that untreated hypertension was associated with the development of dementia.

The study is published in JAMA Network Open.

Why this study is significant

The study’s lead author, neuroscientist Dr. Matthew Lennon, from New South Wales, Australia, explained:

“Previously, studies have found variously that antihypertensive use in late-life may increase dementia risk, decrease it, or have no effect at all. There have been very few large studies that have examined those older than 80 and those in developing countries.”

The risk, he said, is “we are missing the nuances of the physiological and social landscape that may make the difference between an effective and ineffective treatment.”

Dr. Jayne Morgan, cardiologist and clinical director of the Covid Task Force at the Piedmont Healthcare Corporation in Atlanta, GA, who was not involved in the study, said, “Generally speaking, we do not see this type of data— as randomized clinical trials are the gold standard of science, and the majority of these trials are done in the Western hemisphere — inherently excluding data on large swaths of the global population.”

“It may be the case that a treatment that is effective in an [randomized clinical trial] in a developed nation is not effective in a developing nation. Without testing that in a randomized way in the developing context, we will never know,” noted Dr. Lennon.

Why hypertension may promote dementia

While there are various types of dementia, the form that follows hypertension most logically is perhaps vascular dementia.

“That’s basically when people have problems with, or blockages, in the small blood vessels in the brain,” said cardiologist Dr. Cheng-Han Chen, who was also not involved in the study.

Hypertension is a known risk factor for atherosclerosis, or artery disease.

“Artery disease doesn’t have to [pertain to] coronary arteries — it could be arteries in your brain. The connection would be that untreated hypertension causes more atherosclerotic disease in the brain, which then, in turn, leads to more vascular dementia.”
— Dr. Cheng-Han Chen

“Over time, this takes a toll on the blood oxygen supply to the brain,” explained Dr. Morgan.

“Further, there is thickening in the small vessels in the brain, which means that pathological proteins (such as amyloid) cannot be cleared as efficiently,” added Dr. Lennon.

Dr. Lennon also said that “changes in the blood-brain barrier permeability and receptor profiles mean that proteins such as amyloid beta aggregate accumulate, contributing to more rapidly developing dementia.”

Hypertension in the U.S.

The U.S. Center for Disease Control (CDC) reports that nearly half of U.S. adults, 48.1%, have high blood pressure, whether or not they know it. For 2021, it was the primary or contributing cause of 691,095 U.S. deaths, and it is the main driver of heart disease and stroke, the nation’s leading causes of death.

The CDC also says that about one in five Americans who have hypertension are unaware that their blood pressure is unhealthy or even dangerous. High blood pressure has long been known as “the silent killer” because it has no obvious symptoms.

Dr. Morgan suggested a variety of reasons that so many U.S. residents with hypertension remain unaware they have it, including “the growing obesity epidemic, the growing use of the internet and social media for self-diagnosis and therapies, the growing gap in the socioeconomic status and access to healthcare that informs healthy life decisions, the apathy of ‘good enough’ instead of treating to a goal, and a generalized lack of awareness.”

Physicians regularly check patients’ blood pressure at office visits. However, there are many Americans for whom healthcare is financially out of reach.

“The good news is that there are actually a lot of free, public blood-pressure machines,” said Dr. Chen.

“If you don’t have your own, you can go to your local pharmacy, and you can just measure yourself for free there,” he said. The CDC’s web page also has a table that can tell you how to interpret your results if you test yourself using one of these public machines.

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