Your blood pressure is moving all the time. The conventional way to look beyond a single clinic measurement is 24-hour ambulatory blood pressure monitoring, or ABPM. It remains the clinical reference method.
If I asked you what your blood pressure is, could you tell me?
Perhaps you had it checked at the GP six months ago. Perhaps there is a cuff somewhere in a bathroom cupboard. Perhaps, like many people, you remember being told it was 'fine' and haven't thought much about it since.
But here's what I've been thinking about this week.
Your blood pressure is not really 120/80, 130/85 or any other single pair of numbers.
Your blood pressure is moving all the time.
It changes when you stand up. When you walk. When you eat. When you're under pressure. When you recover. When you sleep. When you wake. And, importantly, some of the most revealing changes happen when nobody is measuring it.
So this week I want to talk about the blood pressure you never see.
Let's dive in...
Where insight becomes impact
What I’ve been looking at this week…
There is a phenomenon in medicine called masked hypertension.
This is when your blood pressure looks normal when it is measured in a clinic, but is raised when you are living your normal life.
A 2024 meta-analysis involving 26 studies and more than 129,000 people estimated that masked hypertension affected around 18% of those studied. That's nearly 1 in 5 people! And compared with people with genuinely normal blood pressure, masked hypertension was associated with a 57% higher risk of developing heart disease and a 64% higher risk of death from any cause. PMID: 39722158
That is why a single blood pressure measurement is interesting but a continuous blood pressure pattern during your day to day life can be far more useful.
And then there is night-time.
While you sleep, your nervous system changes gear. Sympathetic drive generally falls, your blood vessels relax and your blood pressure would normally be expected to fall by around 10 to 20% compared with daytime levels. This is known as nocturnal dipping.
Some people don't dip enough. Some barely dip at all. In some people, blood pressure actually rises at night.
Why should you care about what your arteries are doing at 3am?
Because night-time blood pressure carries important prognostic information. European hypertension guidance recognises nocturnal high blood pressure and abnormal dipping patterns as clinically relevant, and night-time blood pressure can predict cardiovascular outcomes extremely well.
Your arteries keep a diary, even when you are asleep.
This is one of those areas where what many people believe about health gets turned on its head. You might assume that the blood pressure reading taken while you are sitting quietly beside a doctor is your 'real' blood pressure. It isn't necessarily.
It's one frame from a 24-hour film.
Track it to hack it.
What I’ve been monitoring this week…
This brings me to a device I use a lot: Hilo.
You know I use devices with my patients, but I am very selective about what I use and why. I want measurements that change what you discover about your biology and, ideally, change what you do next.
Continuous blood pressure monitoring passes that test.
The conventional way to look beyond a single clinic measurement is 24-hour ambulatory blood pressure monitoring, or ABPM. It remains the clinical reference method. You wear a blood pressure cuff on your upper arm that repeatedly inflates during the day and night. It gives valuable information, but anyone who has slept with one will tell you that having a cuff inflate around your arm at regular intervals is not exactly conducive to an undisturbed night's sleep.
This is where wrist-based blood pressure monitoring gets interesting.
HiLo uses an optical sensor at the wrist to take blood pressure measurements automatically throughout the day and night. Rather than having to remember to stop, sit down, position a cuff and press a button, the measurements accumulate in the background.
The technology uses photoplethysmography, or PPG. Light is shone into the skin and the sensor detects tiny changes in blood volume as each pulse travels through the blood vessels. Algorithms analyse the characteristics of those pulse waves and use them to estimate systolic (top number) and diastolic (bottom number) pressure after calibration against a cuff.
Cuffless monitoring remains an evolving field, so I am not yet suggesting we throw away the validated upper-arm cuff or use a wearable reading in isolation to diagnose or alter treatment.
What excites me about the ease of wrist monitoring though is the extra dimension of data it gives me. I can see daytime and night-time averages. I can see trends across days rather than isolated measurements. I can begin to see whether blood pressure actually settles during sleep. And I can look at what happens around the rhythms of real life rather than measuring only when I deliberately decide to measure.
This is the difference between checking your pressure and understanding your pressure.
And there is another layer I am watching with increasing interest: blood pressure variability.
Two people can have exactly the same average blood pressure but very different patterns around that average. One stays relatively stable. The other swings considerably. Research is increasingly linking greater blood-pressure variability with cardiovascular outcomes independently of average blood pressure. A 2024 study using 24-hour ambulatory monitoring found that greater systolic variability ( the top number) was associated with higher mortality and major cardiovascular events over a median 8.3 years of follow-up. PMID 38294177.
The average tells you something. The amplitude tells you something too.
From knowing to doing.
What this means for YOU…
So once you have the Hilo on your wrist, what do you do with the blood pressure information?
First, don't obsess over individual spikes.
Blood pressure is supposed to move. If you rush for a train, find something funny, lift something heavy or feel suddenly stressed, your cardiovascular system needs to respond. A perfectly flat blood-pressure trace would not help you with the demands and joys of daily life.
What you want to look at is the pattern. I call it the 4 Ps: Pressure, Pattern, Peaks and Pause.
The monitor itself doesn't answer those questions. It tells you which questions are worth exploring further.
💼 Case in point: One of my Million Hour Club patients was not remotely worried about his blood pressure. He had had it checked by his GP about a year earlier and had been told it was fine. He felt well. No chest pain. No breathlessness.
As part of the Million Hour Club, my patients receive a new test or piece of health technology each month, so I sent him a Hilo blood pressure wristband to wear for a couple of weeks.
His reaction was essentially: 'I don't really think I need this.'
And then we saw the data.
His blood pressure itself was not dramatically high. What caught my attention was the pattern. At night, when his cardiovascular system should have been moving into recovery and his blood pressure should normally have fallen, it barely dropped.
A single reading in a doctor's surgery did not show him that.
That absence of normal nocturnal dipping did not tell me he had coronary artery disease. But it was a signal that made me look harder at his heart health rather than accepting the reassuring snapshot from the previous year. I arranged further investigation, including a CT coronary angiogram.
It showed a 85% narrowing in one of the major arteries supplying his heart!
He had no symptoms. He had no idea.
Cardiovascular events are more common in the early morning.
Fortunately, we found the narrowing while he had no symptoms.
He now wears his Hilo for two weeks every season.
This is where I think health technology is heading. Less snapshot medicine. More longitudinal medicine.
Less 'what was your blood pressure?' More 'what does your blood pressure do?'
My personal recommendation: wear Hilo for 2 weeks every season (even if you don't have high blood pressure, and especially if someone in your family has high blood pressure or has had a heart attack or stroke.) Discuss whether this approach is appropriate for you with your own doctor.
If you'd like a monitor, here's the link
🎯 If you'd like to make decisions with precision based on your personal data and using devices that are specific for you, then book a private consultation and let's start to decode your health.
Where you’ll find me…
Last week: this was a very special one for me. The launch of my new space at LeRei London. A spectacular private women's only members club in Knightsbridge with longevity at it's heart. Take a look and if you'd like to see me there, just reply to this email!
This week: I'm continuing my brain stimulation case study. Measuring your biological age, cortisol, memory, attention and heart rate variability across six weeks, alongside brain stimulation using Exomind for potentially less brain fog, more clarity, less distraction and better focus. If you are a high performing executive or entrepreneur, experiencing perimenopausal symptoms, taking or stopping GLP-1 medication, or looking for a way to manage ADHD, this may be very helpful for you. Reply to this memo and let's have a conversation - I still have a few spaces for my October cohort.
Next week: I'm delighted to be speaking at the Women's Health Horizons London Summit, changing the landscape of women's health. If you're a doctor, health care professional, researchers, founder, investor, employer or policymaker, come and be part of the conversation to accelerate progress. Secure your ticket here.
A thought to pause on…
“Health hides in patterns long before it announces itself in symptoms.”
Wishing you a wonderful week ahead (that's 168 hours of your Million Hour life!! Dr Alka
The Longevity Quotient is free. It is a short set of questions, not a test, and it shows you where your habits may be shaping how you age.
Take the free LQThis article is general education, not medical advice, and reading it does not create a doctor-patient relationship. If something has been going on for a while, please get it properly looked at by your own doctor.