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STROKE SERIES · ARTICLE 4 OF 12
The risk factors
Who gets a stroke and why.
Most strokes are predictable. Look at the risk factors of the patients who arrive at a stroke unit on any given day, and a pattern shows up — usually a person in their fifties or sixties, often male but increasingly female, with poorly controlled blood pressure, sometimes diabetic, often a smoker, sometimes with an irregular heartbeat nobody knew about, often Black South African. Stroke does not arrive at random. It arrives at the door of people whose body and lifestyle have been building toward it for years.
The reason this matters is that almost every risk factor on the list is modifiable. About 80% of strokes can be prevented by managing eight specific things — most of them already covered in the other Phila Today series, but here gathered into a single picture. The rest of this series is about doing exactly that.
Why this article matters
If you have any of the risk factors below, you can lower your stroke risk significantly. If you have several, the risk-reduction is even bigger because each lever reinforces the others. This article identifies them; articles 7 through 10 of this series cover what to do about each.
The big seven — modifiable risk factors
These are the conditions and habits that you can do something about. Together, they account for more than 80% of stroke risk worldwide and roughly the same in South Africa.
1. High blood pressure
Raises stroke risk by 3 – 4 times. The single biggest cause of stroke in South Africa.
High BP damages the arteries that supply the brain — stiffening them, scarring them, sometimes weakening their walls enough to burst. About half of all strokes in this country are driven by high BP, and most of those are in people whose BP was either undiagnosed or treated badly.
The size of the effect is large. Bringing systolic BP down by 10 mmHg cuts stroke risk by about 30%. There are few interventions in medicine that match this.
What to do: Read the Phila Today High Blood Pressure Series. Get your BP checked. If it is above 130 / 80, talk to your clinic. Take medication every day if prescribed.
2. Diabetes
Roughly doubles stroke risk.
Diabetes damages the small blood vessels of the brain through several mechanisms — chronic inflammation, abnormal blood thickness, accelerated atherosclerosis, and damage to the artery linings. Stroke in diabetics also tends to be more severe and recovery slower.
About 1 in 9 South African adults has diabetes; roughly half don’t know it. Getting tested is free at any public clinic.
What to do: Get a fasting blood sugar or HbA1c test if you haven’t recently. If you have diabetes, follow the Phila Today Diabetes Series and aim for HbA1c below 7%.
3. High cholesterol
Raises ischaemic stroke risk by about 25% per 1 mmol/L of raised LDL.
High LDL (“bad cholesterol”) drives plaque buildup in the carotid arteries (the big arteries in the neck) and inside the brain. Plaque can rupture and trigger a clot. Statins both lower LDL and stabilise existing plaque, which is why they prevent stroke almost as much as they prevent heart attack.
What to do: Get a lipid panel. If you are at moderate or high cardiovascular risk, statin therapy may be recommended. The Phila Today Cholesterol Series covers this in detail.
4. Smoking
Doubles stroke risk. Quitting halves it within 5 years.
Smoking damages artery walls directly, raises BP, lowers HDL, accelerates plaque buildup, makes blood more likely to clot, and triggers AFib in some people. Every cigarette is a small amount of damage; pack-a-day smokers have an effective stroke risk decades older than their actual age.
Vaping is less well studied but is also linked to artery damage and probably raises stroke risk, though by a smaller amount than cigarettes. Don’t use it as a “safer alternative” — use it as a quit-smoking tool only.
What to do: Set a quit date. Use nicotine replacement. Call the CANSA quitline on 011 720 3145. The benefit starts within months.
5. Atrial fibrillation (AFib)
Raises stroke risk by 5 times. Causes about 1 in 5 South African strokes.
AFib is an irregular heartbeat. The upper chambers of the heart (the atria) quiver instead of beating properly, blood pools in them, and clots can form. Those clots can travel to the brain and cause a major stroke.
AFib often has no symptoms at all. Many people only find out they have it after their first stroke. A simple finger-on-the-wrist check at every clinic visit can pick up most cases; suspicious cases get a confirming ECG.
The good news: anticoagulants (blood thinners like warfarin or the newer DOACs — apixaban, rivaroxaban, dabigatran) reduce AFib-related stroke risk by about 60 – 70%. They are widely available in South Africa.
What to do: Ask your clinic to check your pulse for regularity. If you ever feel a fluttering, racing or skipping heartbeat, mention it. People over 65 should have an ECG at least once.
6. Overweight, inactivity, and poor diet
Each independently raises stroke risk by 30 – 50%; together by much more.
Being overweight (especially around the middle), sitting most of the day, and eating a diet high in salt, sugar and saturated fat all push BP, cholesterol and blood sugar in the wrong direction. They also independently raise inflammation in the blood vessels.
30 minutes of brisk walking 5 days a week cuts stroke risk by about 25 – 30% on its own. Losing 5 – 10 kg if overweight cuts it further. The Mediterranean and DASH eating patterns reduce stroke risk by about 20%.
What to do: Start with the 12-week walking plan from the Phila Today High Blood Pressure Series Article 7. Add the food list from the Cholesterol Series Article 5 alongside it.
7. Heavy alcohol use
More than 3 drinks a day doubles stroke risk; binge drinking does it acutely.
Alcohol in moderation has a small protective effect on ischaemic stroke (through raising HDL) but increases haemorrhagic stroke risk. At higher doses, both rise sharply. Binge drinking — five or more drinks in one session — can trigger AFib and acute BP spikes, sometimes leading to a stroke within hours.
What to do: No more than 1 drink a day for women, 2 for men. At least 2 alcohol-free days a week. No binge drinking.
The unmodifiable risk factors
These are the things you can’t change — but it is useful to know whether they apply to you, because they shift the risk benchmark and may justify earlier or more aggressive prevention of the modifiable factors.
Age
Stroke risk doubles every decade after age 55.
Most strokes happen in people over 65. But 20% of South African strokes are in people under 50, and the rate is rising — particularly in women. Stroke is not an old-person condition only.
What it means: The older you are, the more important everything else on this list becomes. Don’t write off symptoms as “just my age”.
Family history
A parent or sibling with stroke before age 65 raises your risk by about 30%.
Some of this is shared genetics — for example, a tendency to higher BP or worse cholesterol metabolism. Some is shared habits — same kitchen, same lifestyle, same culture. Either way, family history tells you to pay attention.
What it means: Get your BP, cholesterol and blood sugar checked earlier. Pay extra attention to the modifiable risks.
Sex
Men have slightly higher stroke risk before 65; women catch up and exceed it after 75.
The story is more complex than it sounds. Women are more likely to have certain stroke types (subarachnoid haemorrhage, cryptogenic stroke), more likely to have stroke around pregnancy, and tend to have worse outcomes than men of the same age — partly because they live longer and have strokes later.
What it means: Women should not assume stroke is “a male problem”. The risks are different but not lower.
Black South African ancestry
Roughly double the average stroke rate.
Black South Africans develop strokes earlier, more severely, and from somewhat different causes than the national average. The biggest single driver is higher rates of high blood pressure — both in prevalence and in poorer control. There are also genetic factors that affect how the body handles salt and how blood vessels respond to BP medication.
What it means: BP screening earlier (from age 18), more aggressive treatment, and particular attention to the salt-cutting work in BP article 6.
The SA-specific and under-discussed risks
Some stroke risk factors are particular to the South African context, or just less commonly talked about. They matter especially for people under 50, where the standard “BP, cholesterol, diabetes” picture often doesn’t fit.
HIV
Untreated HIV raises stroke risk by 2 – 3 times. Modern treatment normalises most of the risk.
HIV drives stroke through several mechanisms — chronic inflammation, accelerated atherosclerosis, and direct viral effects on blood vessels (HIV vasculopathy). Some of the older antiretrovirals also raised cholesterol. Modern HIV care, with viral suppression and newer drug regimens, brings most of the excess stroke risk back close to baseline.
What it means: If you are HIV-positive, stay virally suppressed. Add lipid and BP screening to your routine clinic visits. Many HIV clinics now do this routinely.
Sickle cell disease
In children with sickle cell disease, stroke risk is hundreds of times higher than in the general population.
Sickle cell disease causes the red blood cells to take on an abnormal shape that blocks small arteries. Brain arteries are particularly vulnerable, and stroke is one of the most serious complications, particularly in children. Most stroke risk can be picked up with a special ultrasound (transcranial Doppler) before any stroke happens.
Sickle cell disease is uncommon in South Africa overall but is found in some communities of African ancestry. Children identified at birth or in infancy are usually followed by paediatric haematology.
What it means: Children with sickle cell disease should be in regular specialist care. Transcranial Doppler screening from age 2 is standard internationally.
Pregnancy and the post-partum period
Stroke risk is roughly 3 times higher during and just after pregnancy.
Pregnancy increases the clotting tendency of the blood and changes the cardiovascular system in many ways. The highest-risk period is the first 6 weeks after delivery. Pre-eclampsia (covered in the BP Series Article 11) sharply increases stroke risk, both during and long after pregnancy.
Stroke during pregnancy is uncommon but serious. F.A.S.T. applies in pregnancy as in any other setting — don’t dismiss neurological symptoms.
What it means: Book antenatal care early. Treat pre-eclampsia aggressively. Be alert for stroke symptoms in the weeks after delivery.
The combined oral contraceptive pill
Roughly doubles stroke risk in women under 35, mostly in smokers.
The combined pill (oestrogen + progestogen) raises clotting tendency. The absolute risk is small in healthy young non-smoking women but rises sharply with smoking, migraines with aura, high BP, or family history of clotting. The progestogen-only pill is much safer for stroke risk.
What it means: Discuss contraceptive choice with your clinic, especially if you smoke, are over 35, or have migraine with aura. Many alternatives are stroke-safe.
Cocaine, methamphetamine (“tik”), and other stimulants
Sharply raises stroke risk acutely — minutes to hours after use.
Stimulant drugs cause sudden, severe BP spikes, sometimes burst aneurysms, sometimes acute artery spasm. Stroke in young patients with no other risk factors is often drug-related. Crystal meth (tik) is particularly common in some South African communities and is responsible for a meaningful share of strokes in patients under 40.
What it means: Stop using. If you are struggling, contact SANCA (011 892 3829) or your local addiction service for support.
Tuberculosis (TB)
TB of the brain (TB meningitis) can cause stroke — a particular SA problem.
Tuberculous meningitis is more common in South Africa than in most countries, particularly in HIV-positive children and adults. It can damage the arteries at the base of the brain and trigger ischaemic strokes during or shortly after the acute illness. Most patients who develop TB-related stroke have had recent symptoms — fever, headache, drowsiness — that should have prompted urgent investigation.
What it means: If you are HIV-positive or live with someone who has TB, any persistent unusual headache or new neurological symptom warrants urgent assessment.
Sleep apnoea
Raises stroke risk by about 2 times; treatment cuts it back.
Obstructive sleep apnoea — repeatedly stopping breathing during sleep — raises BP, triggers AFib, and accelerates atherosclerosis. About 1 in 5 South African adults has at least mild sleep apnoea; most don’t know.
The classic signs: loud snoring most nights, a partner who has seen you stop breathing, waking up tired even after 8 hours, falling asleep in the day.
What it means: If two or more of those apply, ask your clinic about a sleep study. Treatment (usually a CPAP machine) significantly reduces stroke risk.
How to estimate your own risk
Most South African clinics now use a 10-year cardiovascular risk calculator (Framingham or SCORE) that combines age, sex, BP, total cholesterol, HDL, smoking and diabetes into a single percentage. The same number predicts both stroke and heart attack risk.
10-year risk Category What it means Under 5% Low Standard preventive measures. 5 – 10% Moderate Lifestyle work; consider medication if BP or cholesterol are raised. 10 – 20% High Lifestyle + medication for BP, cholesterol, sometimes aspirin. Above 20% Very high Aggressive lifestyle + medication for BP, cholesterol, often aspirin, tight diabetes control.
You can ask your clinic for your number. People who know it tend to take prevention more seriously — knowing you have a “23% chance of stroke or heart attack in the next 10 years” focuses the mind in a way that a single high BP reading does not.
Stroke in young people — when the standard picture doesn’t fit
About 1 in 5 South African strokes happen in people under 50. The risk factor picture is different from older patients. The more common causes in young adults:
• The combined contraceptive pill, especially with smoking.
• Pregnancy and post-partum.
• Illicit drugs.
• Sickle cell disease (children and young adults).
• HIV-related vasculopathy.
• Burst aneurysm (subarachnoid haemorrhage).
• Carotid artery dissection — a tear in the lining of one of the neck arteries, sometimes after a sudden neck movement, sometimes spontaneous.
• Heart conditions including patent foramen ovale (a small hole between heart chambers).
• Inherited clotting disorders.
• Rare vasculitis or autoimmune conditions.
Article 11 of this series covers stroke in young people in more detail, including the investigations that are typically done and what the long-term picture looks like.
The bigger picture
Stroke is one of the most preventable serious conditions in medicine. Eighty per cent of strokes happen in people whose risk could have been spotted and addressed years earlier. The other 20% — the unavoidable, the unlucky — are why we also need fast recognition (article 2) and good hospital care (article 5).
The seven modifiable risk factors aren’t separate from each other. They are connected — high BP and diabetes share root causes; smoking damages everything; weight drives BP, cholesterol and blood sugar all at once. Improvements in one tend to cascade across the others. This is the engine of the rest of this series — and of the Phila Today archive more broadly.
The next article in the series — which you may already have read — covers what happens at the hospital when a stroke hits despite your best prevention. Article 6 picks up the recovery story.
Where to get more help
Heart and Stroke Foundation South Africa — heartfoundation.co.za · 021 422 1586 — has a free 10-year heart-disease risk calculator.
Your nearest public clinic — for BP, cholesterol, blood sugar and pulse-rhythm checks. All free.
Phila Today High Blood Pressure Series, Cholesterol Series, and Diabetes Series — companion reading for the biggest three modifiable stroke risks.
Phila Today Stroke Series — next: what happens at the hospital (article 5).
Phila Today · Article 4 of 12 in the Stroke Series