Stroke: Warning Signs, the FAST Test and Prevention

Stroke is one of the leading causes of death and the leading cause of long-term disability in adults. Its defining feature is that outcome depends almost entirely on how fast help arrives: restoring blood flow within the first hours can give someone back their speech and movement, while the same treatment a day later is useless. Recognising a stroke in under a minute is therefore not specialist knowledge — it is a basic skill, like knowing how to call the fire service.

The FAST test — 60 seconds#

Letter	What to check	Sign of stroke
F — Face	Ask them to smile or show their teeth	One corner of the mouth droops, half the face doesn't move
A — Arms	Ask them to raise both arms and hold for 10 seconds	One arm drifts down or cannot be raised
S — Speech	Ask them to repeat a simple sentence	Slurred speech, jumbled words, or can't understand you
T — Time	Any of the above	Call emergency services immediately; note the onset time

Beyond the classic three, other sudden symptoms matter: abrupt loss of vision in one eye or loss of half the visual field, sudden severe dizziness with loss of balance, numbness down one side of the body, or "the worst headache of my life" — characteristic of subarachnoid haemorrhage. What unites all of them is suddenness. A neurological deficit that appears within seconds or minutes always warrants emergency care.

Why minutes matter#

In ischaemic stroke a clot blocks an artery and part of the brain loses its oxygen supply. The core of the territory dies quickly, but around it lies the penumbra — tissue with reduced but preserved flow. That is what can be saved if circulation is restored in time. By Saver's calculation, in a typical large-vessel stroke each minute costs roughly 1.9 million neurons and 14 billion synapses — an hour ages the brain by 3.6 years.

That drives the treatment logic. Thrombolysis — intravenous clot-dissolving medication — works best within 4.5 hours. Thrombectomy — mechanical clot removal via catheter — is used for large-vessel occlusion within 6 hours, and up to 24 hours in patients selected by CT or MR perfusion imaging. Both require a hospital with a stroke unit, and both require ruling out bleeding on CT first, because in haemorrhagic stroke thrombolysis is lethal.

Two types of stroke#

Type	Share	Mechanism	Notes
Ischaemic	about 85 %	Clot or embolus blocks an artery	Thrombolysis and thrombectomy possible
Haemorrhagic	about 15 %	Vessel ruptures, blood enters brain tissue	Usually on a background of high blood pressure; thrombolysis contraindicated
Subarachnoid	subtype of haemorrhagic	Ruptured aneurysm	'Worst headache of my life', vomiting, light sensitivity

A distinct source of ischaemic stroke is atrial fibrillation. In this arrhythmia blood stagnates in the left atrial appendage, a clot forms there and is then carried to the brain. Strokes caused by fibrillation tend to be more severe. The good news: appropriate anticoagulation cuts that risk by roughly two thirds, making detection of the arrhythmia one of the highest-yield preventive measures available.

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What you can change#

The INTERSTROKE study across 32 countries found that ten factors explain about 90 % of population stroke risk. Nearly all of them are modifiable.

Risk factor	Contribution	What to do
Hypertension	largest single factor	Hit target pressure, monitor regularly, treat
Smoking	high	Complete cessation; risk falls within the first years
Physical inactivity	high	150–300 minutes of moderate activity per week
Diet	high	Mediterranean pattern, less salt
Obesity (especially abdominal)	moderate	5–10 % weight loss
Diabetes	moderate	Glycaemic control
Alcohol	moderate	Reduce; no safe level established
Lipids	moderate	Lower LDL, statins where indicated
Atrial fibrillation	moderate	Detection and anticoagulation as prescribed
Psychosocial stress	moderate	Sleep, routine, stress management

Hypertension is the clear leader: every 10 mmHg reduction in systolic pressure lowers stroke risk by roughly a quarter. And since hypertension is almost always symptomless, the only way to find it is to measure your blood pressure rather than wait for a headache.

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After a stroke or TIA#

Recovery starts in hospital and continues for months. The steepest gains come in the first three to six months, but improvement remains possible later — neuroplasticity responds to consistent practice for years. Standard rehabilitation includes physiotherapy, speech and language therapy for communication and swallowing, occupational therapy for daily living skills, and psychological support: post-stroke depression affects roughly a third of patients and impairs recovery.

Secondary prevention matters as much as acute treatment: blood pressure control, antiplatelet or anticoagulant therapy where indicated, statins, smoking cessation and regular activity cut recurrence substantially. Recurrent strokes account for a large share of severe disability.

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The bottom line#

A stroke can be identified in a minute with FAST: a drooping face, a weak arm, disturbed speech — any one of these means calling emergency services immediately and noting the time symptoms began. Give no medication, water or food while waiting. Symptoms that resolve on their own are not reassurance but a TIA, signalling high stroke risk within days. Prevention, meanwhile, is largely in your hands: blood pressure, not smoking, movement, diet and detecting atrial fibrillation cover most of the modifiable risk.