Clare Wilson
Health reporter, New Scientist - May 2024
This week, my thoughts have been turning to blood pressure, for two reasons. Firstly, more than one of my friends has recently learned they have higher-than-desirable blood pressure and are wondering about any alternatives to starting medication.
 
The second reason is a study that came out this week on an interesting new approach that helped people reduce their blood pressure under medical guidance with fewer visits to the doctor.
 
I’ll get to the study shortly, but first let’s take a quick look at what blood pressure measurements actually signify.
 
As it sounds, blood pressure is just the pressure that blood exerts on artery walls as it sloshes around the body. It reflects the force with which the heart pumps, the amount of blood in circulation and the way blood vessels can dilate or contract.
 
We measure it with two numbers: the higher, called systolic pressure, is when the heart is pumping, while the second, diastolic pressure, occurs between heartbeats. An optimal reading is generally seen as between 120/80 and 90/60 millimetres of mercury (mmHg).
 
Initially, high blood pressure, also called hypertension, was thought to trigger strokes and heart attacks only at very high levels. By the 1960s, it emerged that, over the long-term, even mild hypertension could cause these events, as well as doing other damage, such as hardening blood vessels, hence causing dementia and kidney disease.
 
Fortunately, there are several types of medicines that can reduce blood pressure — known as antihypertensives — and randomised trials have shown that, as expected, they lower the risk of heart attacks and so on. With more than a third of adults having high blood pressure in most high-income countries, antihypertensives are among the greatest advances of modern medicine in terms of the number of lives saved.
 
Nevertheless, the question remains for those using these drugs as to how much they should reduce their blood pressure. To get it low enough, people may end up on several medications, taking multiple tablets several times a day.
 
These can have various side effects, plus any antihypertensive regimen can sometimes be too effective — blood pressure tends to vary over the day, so sometimes it can get too low. This can make people feel dizzy and cause falls, which can be particularly serious for older people.
 
In the UK, doctors generally aim for 140/90 or 150/90 in people older than 80, partly because blood pressure tends to rise naturally with age. In the US, the target was lowered to 130/80 in 2018 for all ages. This suggests that either US doctors are lowering blood pressure too much or UK medics aren’t reducing it enough.
 
Drug alternatives
Antihypertensive drugs aren’t the only option, though. If someone who is overweight has high blood pressure, they are usually advised to also try losing weight though diet and exercise.
 
The trouble is, it is extremely hard to shed weight and keep it off this way. In fact, about nine out of 10 people who lose weight by dieting end up putting it back on.
 
Possibly less well known is that other lifestyle changes can be highly effective. The number one dietary intervention for blood pressure is lowering salt intake.
 
I’m usually sceptical of dietary research, as much of it is based on poorly designed population studies. In contrast, the finding that lowering salt intake works well at reducing blood pressure has been shown in several well-designed randomised trials, with about the same magnitude of effect as taking an antihypertensive.
 
There is another type of lifestyle change that works well at lowering blood pressure: a particular kind of exercise known as isometric strength training.
 
This involves holding a strenuous position for as long as possible. The two best known examples are doing the “plank” – where you suspend yourself above the floor horizontally, resting on your toes and forearms or palms – and doing “wall squats”, where you take a seated position with your back against a wall.
 
It isn’t clear why this form of exercise is better than others, but one idea is that when the muscles are contracted, blood flow reduces, then when the person finishes holding the position, blood rushes back, sending signals that tell blood vessels to relax. Long-term, this leads to lower blood pressure. However anyone with uncontrolled high blood pressure should consult their doctor before beginning such exercises because during the contraction, blood pressure temporarily rises.
 
Finally, we come to the most recent study of a newer approach to blood pressure management. Usually people need to keep returning to their doctor, who adjusts their medication dose until their readings get to the desired level.
 
Yet when it comes to type 2 diabetes, people are encouraged to adjust their dose of insulin or other medicines themselves, depending on their daily blood sugar levels. Some Spanish doctors wondered if people could do the same for their blood pressure medicines?
 
In this trial, people who were given blood pressure monitors and guidance on how to change their drug doses achieved readings that were slightly better than those who had to keep returning to their doctor to have their doses adjusted.
 
I love this result, as I’m all in favour of people taking charge of their own health, with medical guidance and support. In countries such as the UK, blood pressure monitors are available for anyone to use in many primary care clinics or pharmacies. What is stopping you finding out your own blood pressure today?