Stroke: Why Every Minute Counts, the FAST Test, the 10 Risk Factors Behind 90% of Strokes, and Why Kidney Patients Face 2–3 Times the Risk

How common and how serious

The World Stroke Organization estimates about 12 million new strokes and 6.5 million stroke deaths a year, and that 1 in 4 adults over 25 will have a stroke in their lifetime [1]. Stroke is the world's second leading cause of death and third leading cause of disability; incidence is higher in Asia than in Europe or North America, with a larger share of haemorrhagic stroke (about 20–30% vs 10–15%) [1].

Two main types [2]:

• Ischaemic stroke (≈85%): a vessel is blocked by a clot — from atherosclerosis of brain or carotid arteries, or a clot thrown from the heart in atrial fibrillation.
• Haemorrhagic stroke (≈15%): a vessel ruptures, most often from long-standing uncontrolled hypertension.

Transient ischaemic attack (TIA, "mini-stroke"): the same symptoms resolving completely within 24 hours (usually within an hour). A TIA is not a near miss; it is the strongest warning — stroke risk in the next 90 days is about 10–17%, half of it within 48 hours [2].

FAST: 1.9 million brain cells die every minute

In ischaemic stroke, about 1.9 million neurons die each minute [3]. Intravenous thrombolysis (alteplase/tenecteplase) must be given within 4.5 hours of symptom onset; mechanical thrombectomy for large-vessel occlusion can extend to 24 hours with imaging selection — but earlier is always better, and every 15-minute delay reduces the chance of a good outcome [2][3].

The FAST test [1][2]:

Also be alert to other sudden symptoms: sudden loss or blurring of vision in one or both eyes, sudden severe headache ("worst of my life"), sudden loss of balance or difficulty walking, numbness on one side of the body [2].

Three common mistakes:

1. "Let's wait and see if it passes" — seek care even if TIA symptoms resolve.
2. Driving yourself or being driven by family — an ambulance goes straight to a stroke-ready hospital and pre-alerts the team.
3. Giving food, drink or aspirin — choking risk, and aspirin worsens a haemorrhagic stroke.

Ten risk factors explain 90% of strokes

INTERSTROKE (32 countries, nearly 27,000 participants) found that ten modifiable risk factors account for about 90% of strokes [4]:

In Asian populations, hypertension and alcohol contribute even more [4].

Prevention: how much each step helps

Primary prevention (no prior stroke), AHA/ASA 2024 [5]:

• Blood pressure: each 10 mmHg lower systolic cuts stroke risk by about 27–30%; target <130/80. The highest-yield action.
• Atrial fibrillation: anticoagulation (DOACs) lowers stroke risk by about 64%; check your pulse or have an ECG regularly from age 65.
• Exercise: ≥150 min/week moderate intensity lowers risk by 25–30%.
• Diet: the Mediterranean diet (PREDIMED) cut stroke by about 40%; less sodium, more fruit and vegetables.
• Lipids: statins lower stroke by about 20% in high-risk people.
• Diabetes: glucose control helps small-vessel disease; SGLT2i/GLP-1 RA add cardiovascular protection.
• Stop smoking, limit alcohol (≤1–2 drinks/day).
• Aspirin is not recommended for primary prevention in people without cardiovascular disease (bleeding outweighs benefit) [5].

Secondary prevention (after stroke/TIA), AHA/ASA 2021 [2]:

• Antiplatelet therapy (aspirin ± short-term clopidogrel) or anticoagulation if AF.
• High-intensity statin, LDL target <70 mg/dL.
• Blood pressure <130/80.
• Symptomatic carotid stenosis ≥70%: endarterectomy or stenting.
• Screen for and treat sleep apnoea.
• Start rehabilitation early; most gains occur in the first 3–6 months, but improvement continues beyond.

Kidney patients: why the risk is 2–3 times higher

Stroke risk in CKD is about 2–3 times the general population and 5–10 times in dialysis, with a particularly high share of haemorrhagic stroke [6]. Why:

• High rates of hypertension, diabetes and atrial fibrillation (10–25% of dialysis patients have AF).
• Vascular calcification and endothelial dysfunction: uraemic toxins, phosphate and parathyroid abnormalities accelerate arterial disease.
• Platelet dysfunction: CKD increases both clotting and bleeding tendency — the central therapeutic dilemma.
• Blood-pressure swings during dialysis: intradialytic hypotension can cause watershed ischaemia.
• Anaemia, chronic inflammation, oxidative stress.

Practical points [2][6]:

• Blood-pressure control is the most effective stroke prevention for kidney patients, but dialysis targets must be individualised to avoid intradialytic hypotension.
• For anticoagulation decisions in CKD with AF, see this site's atrial fibrillation article; evidence is weak at eGFR <15 or on dialysis, requiring joint cardiology–nephrology assessment.
• CKD is not a contraindication to thrombolysis in acute stroke, though bleeding risk is somewhat higher; tell the emergency team about your kidney disease, dialysis schedule and medications.
• Post-stroke rehabilitation and drug therapy in dialysis (statin benefit evidence is weaker) need individual tailoring.
• Transplant recipients: tacrolimus-related hypertension and post-transplant diabetes are stroke risk factors — controlling them is prevention.

When to seek care immediately

Call emergency services (do not go on your own): any FAST sign; sudden severe headache; sudden loss of vision in one or both eyes; sudden severe vertigo with unsteadiness or double vision; even if symptoms resolve within minutes.

Within 24 hours: brief FAST-type symptoms in the past few days that were not assessed (the high-risk TIA window).

Routine appointment: multiple risk factors never assessed; over 65 and never had an ECG; BP persistently >140/90.

Questions to ask your doctor

1. What are my stroke risk factors, and which should be tackled first?
2. Do I need a carotid ultrasound or an ECG?
3. Do I (and my family) know FAST? Where is the nearest stroke centre?
4. (CKD) What is my BP target? What if my pressure drops too low on dialysis?
5. (AF) Do I need an anticoagulant?

References

1. World Stroke Organization. Global Stroke Fact Sheet 2022. Feigin VL, et al. Int J Stroke. 2022;17(1):18–29. https://doi.org/10.1177/17474930211065917
2. Kleindorfer DO, et al. 2021 AHA/ASA Guideline for the Prevention of Stroke in Patients With Stroke and TIA. Stroke. 2021;52(7):e364–e467. https://doi.org/10.1161/STR.0000000000000375
3. Saver JL. Time is brain—quantified. Stroke. 2006;37(1):263–266. https://doi.org/10.1161/01.STR.0000196957.55928.ab
4. O'Donnell MJ, et al. INTERSTROKE. Lancet. 2016;388(10046):761–775. https://doi.org/10.1016/S0140-6736(16)30506-2
5. Bushnell C, et al. 2024 AHA/ASA Guideline for the Primary Prevention of Stroke. Stroke. 2024;55(12):e344–e424. https://doi.org/10.1161/STR.0000000000000475
6. Kelly DM, Rothwell PM. Prevention and treatment of stroke in patients with chronic kidney disease: an overview of evidence and current guidelines. Kidney Int. 2020;97(2):266–278. https://doi.org/10.1016/j.kint.2019.09.024

This article compiles publicly available medical information for educational purposes only. It is not medical advice and has not been reviewed by a practising physician. For any health or medication question, consult a qualified professional. For chest pain, sudden breathlessness, one-sided weakness or slurred speech, call your local emergency number or go to the emergency department immediately.