Health
Stroke Risk Factors: Which Ones You Can Actually Measure and Change
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You have probably seen the list. Age, blood pressure, smoking, cholesterol, family history. You scan it, recognise a few that might apply to you, and come away no clearer than before. Which ones actually matter for you? And what are you meant to do, beyond "lower your risk"?
Stroke can feel like an older person's problem, something to think about later. But the processes behind it build quietly over decades, often from your 30s and 40s. The reassuring part is that most of what drives stroke risk can be measured, and a lot of it can be changed, once you are working from your own numbers rather than a generic list. That is what this piece is about: the factors you can measure, the ones you can change, and how to tell the difference.
The two types of stroke risk factor
Stroke risk factors split into two groups: the ones you cannot change, and the ones you can. Both matter for understanding your picture, but only one group gives you something to act on.
Underneath the long lists, almost all stroke traces back to three processes. A useful shorthand is pressure, particles and clotting.
Pressure is blood pressure. Across large international studies, it is the single factor most strongly linked to stroke [1, 3]. Sustained high pressure slowly damages the lining of your arteries and, over years, can weaken the small vessels in the brain.
Particles are the cholesterol-carrying particles in your blood. When there are too many, they lodge in the artery wall and build up the fatty plaque that narrows arteries and can later become the surface a clot forms on.
Clotting is the third route, and it is the step most people miss. A large share of strokes are really a clot problem: a clot forms somewhere, breaks loose and blocks an artery feeding the brain. It can form on existing plaque, or because blood is pooling where it should not, as happens with the irregular heartbeat called atrial fibrillation.
Factors you cannot change
Some factors are fixed. Knowing them helps you focus on the rest [2, 3]:
Age. Risk climbs as arteries naturally stiffen over time.
Family history. A parent or sibling who had a stroke raises your own risk.
Ethnicity. Risk is higher in some groups, including people of Black, African-Caribbean and South Asian heritage.
Sex. Men have a higher risk of stroke than women through midlife. That gap narrows after menopause, as the protection oestrogen provides falls away.
Inherited factors. Some people carry a raised, largely genetic cholesterol particle called Lp(a) [6], or an inherited tendency to clot. Neither can be changed, but both can be picked up with a one-off blood test.
Factors you can change or manage
The list you can act on is longer than most people expect:
Blood pressure, the single biggest lever, and often the first to drift unnoticed.
Your cholesterol particles, which respond to diet, activity and, where needed, medication.
Blood sugar and insulin sensitivity, which often quietly influence blood pressure and cholesterol particles.
Smoking, which worsens pressure, particles and clotting all at once.
Weight, activity, alcohol and sleep, the daily inputs that feed into the rest.
These are not five separate problems. Insulin sensitivity in particular sits upstream of both blood pressure and cholesterol particles, which is why improving it can move more than one number at once.
Which risk factors you can measure
This is where a generic list stops being useful and your own numbers take over. A named risk factor tells you very little until you know where you personally sit on it. Most of the factors you can change can be measured directly.
Blood pressure. Simple to measure, but a single reading in a clinic tells you little. It moves through the day, and stress can push it up in ways one snapshot never captures. A truer picture comes from readings taken over time.
Cholesterol, measured properly. A standard cholesterol test is a rough guide. A more precise measure is ApoB, which counts the actual particles that drive arterial risk. In some people, particularly those with early insulin resistance, a standard cholesterol result can look fine while the particle count is quietly high [7]. ApoB catches what the usual test can miss.
Lp(a), once. This inherited particle barely changes across your life, so it only needs measuring once. It is worth knowing, because a raised level is fairly common and completely invisible without a test [6].
Blood sugar, over time. A single glucose reading is a moment in time. Markers that reflect your blood sugar over weeks or months give a fuller read, and a handful of related blood markers can flag insulin resistance earlier than glucose alone.
Clotting. Where it is relevant, a blood test can flag an inherited tendency to clot that you would otherwise never know you carried.
Why the usual stroke risk lists fall short
Generic lists have two weaknesses. They are built for populations, not for you, and they treat each factor as a simple yes or no.
Take "within range". A blood result inside the normal range only means you sit within the middle of whatever population the lab used to set that range, a group defined mostly by not having a diagnosed condition. It does not mean the level is optimal for you. Standard cholesterol can read normal while your particle count is high. Normal is not the same as optimal.
Most factors are not on or off, either. They sit on a spectrum, and they move over time. A one-off reading misses the trend, which is often what matters most. And the pieces rarely talk to each other: a wearable, a blood test from last year and your GP have never been in the same place.
More testing is not automatically better, though. Some markers get measured because they can be, not because they change anything. Blood levels of homocysteine are a good example: they are linked to stroke, but the evidence that acting on them helps is not settled [8], so measuring it can add noise rather than insight.
What your personal risk picture looks like
Your risk is not a single number, it is a combination. Several borderline factors can add up to more than any one factor on its own, and some combinations may push harder together than either would alone. Exactly how they combine in a given person is still an open question, which is precisely why a personal picture beats a checklist.
Trajectory matters more than a single reading. For the factors that move, like blood pressure, cholesterol particles and insulin sensitivity, what counts is cumulative exposure over years, not the number on the day you happened to test. Someone whose particle count has quietly sat high for fifteen years carries a different risk from someone who crossed the same line last month, even though a single test would look identical. Tracking a marker over time adds detail a snapshot cannot.
This is also where risk calculators like QRISK show their limits. They are genuinely useful, folding in things like ethnicity, migraine and irregular heart rhythm that routine bloods miss [5]. But they estimate risk over the next ten years, a window that tends to flatter younger people whose risk is building for later. They also lean on standard cholesterol rather than particle count, and leave out inherited factors like Lp(a) [14]. Someone in their 30s or 40s can get a low ten-year score and still be on a rising long-term trajectory.
What you can do about the factors you control
You cannot change your genetics, but you can change most of what actually drives risk. A rough order helps.
If you smoke, stopping comes first. It is the single change that does the most, because it improves blood pressure, cholesterol particles and clotting at the same time.
After that, blood pressure and insulin sensitivity are closely linked, so working on insulin sensitivity is often the fastest way to help both. Diet does much of the work: shifting from processed, salt-heavy food towards whole foods rich in vegetables, legumes, nuts and seeds raises potassium and lowers sodium, and that balance is one of the better-supported influences on blood pressure for people without kidney problems [13]. Sleep and stress feed into the same system.
Cholesterol particles respond to that same upstream fix, then to diet, with fibre and saturated fat as the main levers. People vary in how much saturated fat affects their particle count, so it is worth checking rather than assuming. Where diet and lifestyle are not enough, often when the cause is largely genetic, medication is the next step, and that is a conversation with a clinician rather than a solo decision.
As a rule of thumb: the lifestyle factors are yours to manage. Once a genetic result is in hand, or lifestyle changes have not moved a number enough, that is the point to bring in a clinician.
How Calibre fits
Much of the problem is not effort, it is fragmentation. Your family risk, your blood pressure, your bloods and your wearable data have never been looked at together, and a one-off test never shows a trend.
Calibre brings those together, from your family history and blood results to your blood pressure and the data from your wearables, into one picture, then works out which factors are driving your personal risk and what to do about them, with clinicians interpreting the data rather than leaving you to. The factors that move are retested over time, so you are following a trajectory rather than guessing from a single reading. It is clinician-led, with a CQC-regulated clinical partner. The aim is straightforward: from understanding where you stand today to improving your long-term health.
Common questions
What are the main risk factors for a stroke? High blood pressure is the largest, followed by your cholesterol particles, smoking, blood sugar and insulin resistance, and an irregular heart rhythm called atrial fibrillation. Alongside these sit the fixed factors: age, family history, ethnicity, and inherited particles like Lp(a) [2, 3].
Which stroke risk factors can I actually change? Blood pressure, your cholesterol particles, blood sugar and insulin sensitivity, smoking, weight, activity, alcohol and sleep. Inherited factors like Lp(a) and a genetic tendency to clot cannot be changed, but knowing you carry them changes how closely you manage everything else.
What is the single biggest risk factor for stroke? High blood pressure. It is the factor most strongly linked to stroke in large studies, and because it usually causes no symptoms, it is often the one drifting unnoticed [1, 3].
Which blood tests show the risk factors I can measure? ApoB gives a more precise read than a standard cholesterol test, Lp(a) is a one-off test worth doing once, and blood sugar is best judged with markers that reflect weeks or months rather than a single reading, alongside markers that flag insulin resistance. Where relevant, a clotting screen can be added. Blood pressure is not a blood test but belongs on the list, tracked over time.
Can I understand my risk factors of stroke without seeing a specialist? To a point, yes. The measurements are standard and a GP can start you off. What adds the most is interpreting them together and working out which matter for you, which is where clinician input helps. This is about understanding your risk, not diagnosing yourself.
Do stroke risk factors differ for women? Yes. The combined pill and oral HRT can raise clotting risk, because oestrogen taken by mouth passes through the liver and increases clotting factors [9]; HRT through the skin largely avoids that. Pregnancy, and especially the weeks after birth, also raise clotting risk [11]. Migraine with aura is linked to stroke, and that link is stronger when combined with the pill or smoking [12]. These are worth discussing with a clinician, not reasons to stop anything on your own.
How is a stroke risk score like QRISK worked out? It is a statistical model built from population data, using age, blood pressure, a cholesterol ratio, smoking, conditions such as diabetes and atrial fibrillation, and ethnicity, to estimate risk over ten years [14]. It is useful, but it leaves out ApoB and Lp(a) and can under-read long-term risk in younger people. Guidelines say it should not be used for people with inherited high cholesterol, who are treated as high risk from diagnosis [5].
How often should I check the factors I can measure? It depends on the marker. Lp(a) needs measuring only once, because it barely changes. Blood pressure, cholesterol particles and blood sugar are worth checking often enough to see a trend rather than a single point in time.
References
O'Donnell MJ et al. Global and regional effects of potentially modifiable risk factors associated with acute stroke in 32 countries (INTERSTROKE): a case-control study. Lancet 2016. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(16)30506-2/abstract
NHS. Causes of a stroke. https://www.nhs.uk/conditions/stroke/causes/
Stroke Association. Risk factors. https://www.stroke.org.uk/stroke/types/risk-factors
British Heart Foundation. Stroke: causes, symptoms and treatment. https://www.bhf.org.uk/informationsupport/conditions/stroke
NICE. Cardiovascular disease: risk assessment and reduction, including lipid modification (NG238). https://www.nice.org.uk/guidance/ng238/chapter/Recommendations
European Atherosclerosis Society consensus statement on lipoprotein(a). European Heart Journal 2022. (URL to verify)
Sniderman AD et al. ApoB versus LDL-C, and discordance in insulin resistance. Journal of Clinical Lipidology 2014. (URL to verify)
Casas JP et al. Lancet 2005; HOPE-2, New England Journal of Medicine 2006. Homocysteine-lowering and stroke risk. (URL to verify)
Vinogradova Y et al. Use of hormone replacement therapy and risk of venous thromboembolism. BMJ 2019. (URL to verify)
de Bastos M et al. Combined oral contraceptives and risk of venous thromboembolism. Cochrane 2014; WHO Collaborative Study, Lancet 1996. (URL to verify)
Kamel H et al. Risk of a thrombotic event after the six-week postpartum period. New England Journal of Medicine 2014. (URL to verify)
Schürks M et al. Migraine and cardiovascular disease. BMJ 2009; Chang CL et al. BMJ 1999. (URL to verify)
Sacks FM et al. DASH-Sodium. New England Journal of Medicine 2001; Neal B et al. SSaSS. New England Journal of Medicine 2021. Potassium, sodium and blood pressure. (URL to verify)
Hippisley-Cox J et al. QRISK3 derivation. BMJ 2017. Confirms the variables used, and the absence of ApoB and Lp(a). (URL to verify)
