12 Nov 2023

Julian Paton: Blood pressure and links to dementia

From Sunday Morning, 11:32 am on 12 November 2023

High blood pressure affects one-third of adult New Zealanders and disproportionately more Māori and Pacific people.

It’s the biggest risk factor for cardiovascular disease – the leading cause of death here and globally – and researchers are now studying its links to dementia in later life.  

It’s clear we don’t yet know everything about controlling high blood pressure, says Professor Julian Paton from the University of Auckland’s Faculty of Medical and Health Sciences, but research he is leading aims to find a new way. 

Checking blood pressure. (Photo by SCIENCE PHOTO LIBRARY / R3F / Science Photo Library via AFP)


Where does blood pressure come from?

Blood pressure is defined as the force that's exerted on your blood vessels, particularly the arteries, he says.

“It's a really important force, because what it does is it drives blood flow. And what the body cares about, what the tissues, the organs care about is blood flow, blood flow is important, because that's what's going to supply the tissues with what they need, which is oxygen and glucose.”

Why a one medicine fits all approach is wrong

“All drugs to treat blood pressure are tested and have been tested and they've been around for many years, we haven't had a new antihypertensive drug to treat blood pressure for about 20 years. All these drugs that we have at our disposal have all been tested on white, Caucasian men. Why therefore would they work on women?  Why would they therefore work on our Maori or our Pacific people in and around Auckland or our Indians or our Chinese? That's where we're at with blood pressure treatment, I'm afraid.

“What we really do need is to start to adopt some tests, some genetic profiling tests, that would allow us to better predict through genetics, what drug an individual will respond to.”

Why controlling BP is important

“If you start off with a condition such as high blood pressure, which is asymptomatic, you can't feel it, you can't sense it, there's no pain involved. Why would you then end up taking a bunch of tablets that actually make you will make you feel ill.

“This is the problem that the medical profession is facing in terms of convincing patients that you must keep your blood pressure under control, because it is the source of many evils to come.

“I'm talking about cardiovascular risks such as heart failure, heart attacks, stroke, renal damage, all these things will result from high blood pressure, atrial fibrillation is another one.

“So, knock it on our head early is the message.”

To what extent is high blood pressure causal with dementia?

“Our hypothesis has been that high blood pressure is a result of narrowed arteries going into the brain and that triggers high blood pressure.

"So, coming back to the dementia issue, dementia being a result of poor blood pressure. We have to be very careful about treating blood pressure, because if you push blood pressure down pharmacologically by drugs, and you have high resistance of those arteries taking blood into the brain, then you're losing that force that you need, you're losing that blood pressure force that enables sufficient blood flow to get into the brain.

“There is an emergence of crossroads between dementia and high blood pressure. And we've known this for quite some time, because the use of what's called ACE inhibitors (angiotensin converting enzyme inhibitors), these drugs are used to treat both dementia and lowering blood pressure.

‘And those drugs can help improve blood flow into the brain. Having sufficient flow, blood flow into the brain helps clearance of this plaque material, which we all know is associated with dementia.”

Research into a new way of treating high BP

“We've just identified a detector in the brain that is sensing blood flow. And this is unique, novel, revolutionary. That detector automatically activates nerves coming out of the brain to blood vessels, every blood vessel in your body has a nerve from the brain going to it and that nerve is able to either open up the vessel or shrink it - we call that dilatation or constriction.

“When you activate those nerves, you constrict blood vessels, those nerves are called sympathetic nerves. And they're all part of the fight and flight defence response. They work very quickly. They're very powerful.”

“Now, what we've seen in patients with high blood pressure is that the activity in those nerves is abnormally very high. Those nerves are activated by anxiety, they're activated through depression. And we know patients with anxiety, depression also have high blood pressure.

“It's these nerves that we're really interested in, none of our frontline, antihypertensive medications, do anything to reduce the activity in those nerves.

“And that would explain why it is we have so many patients that are taking their drugs that still remain with some hypertension, because those drugs are not really addressing the cause, they're addresing the symptom.

“They may help dilate the blood vessel, but they're not reducing this nervous activity.”

Blood pressure check

Photo: Pexels

Implications for future therapy

“Even if you're on drugs, you still remain at risk of a cardiovascular event. And we believe that that is due to the fact that we're not controlling this nervous activity, this excessive nervous activity.

“Not only have we found this novel detecting system in the brain, but we've also detected sensory organs in the periphery and these are called carotid bodies, and they are located on the arteries just beneath the brain.

“So, it's just before those arteries go into the brain, they're very small, they're about the size of a rice grain, one on each side. They sit next to the carotid arteries, and they detect the levels of oxygen.

“And we've recently discovered they also detect the levels of glucose.

“And so many patients in the real world not only have high blood pressure, but they have high blood sugar. And we found therefore a nodal point, which we can target therapeutically, to try and alleviate symptoms of high blood pressure and high blood sugar.”

Trials to test the new therapy

“It's going to be performed with colleagues in Poland, who are experts at doing what we call first-in-human trials.

“We've identified a mechanism, we've got a drug, that drug has been approved by the European Medicines Association.

“And this is a brand-new drug. And, hopefully by the middle of next year, we will know if that drug is able to control the activity in these nerves and lower blood pressure, because if it is, this then gives a new piece of armoury to combat high blood pressure.”