Understanding Strokes: A Comprehensive Guide

Page last updated: July 20, 2025

A stroke, clinically known as a cerebrovascular accident (CVA), is a medical emergency that occurs when the blood supply to part of the brain is interrupted or severely reduced. This deprives brain tissue of essential oxygen and nutrients, causing brain cells to begin to die within minutes. Globally, stroke is the second leading cause of death, responsible for an estimated 6.6 million deaths annually, and is a leading cause of long-term disability [1].

Thinking of a stroke as a "brain attack" is crucial because it highlights the same urgency as a "heart attack." Quick recognition and immediate medical intervention are paramount to improving outcomes. The phrase "Time is Brain" is used by neurologists because, on average, a person loses 1.9 million neurons for each minute a stroke is left untreated [2].

1.The Two Main Types of Stroke

Strokes are broadly categorized based on their underlying cause: a blockage or a bleed.

A. Ischemic Stroke (The "Blockage")

This is by far the most common type, accounting for approximately 87% of all strokes [3]. An ischemic stroke is analogous to a blockage in a pipe, where a blood clot obstructs blood flow to the brain.

  • Thrombotic Stroke: A blood clot (thrombus) forms within one of the brain's arteries, typically in those already narrowed by atherosclerosis (plaque buildup).
  • Embolic Stroke: A blood clot or debris (embolus) forms elsewhere in the body—often the heart—and travels to lodge in a narrower brain artery. Atrial Fibrillation (AFib) is a common cause.

B. Hemorrhagic Stroke (The "Bleed")

This type occurs when a blood vessel ruptures. While accounting for only 13% of cases, it is responsible for more than 40% of all stroke-related deaths [4].

  • Intracerebral Hemorrhage: Bleeding occurs directly inside the brain tissue, often caused by chronic high blood pressure.
  • Subarachnoid Hemorrhage: Bleeding occurs in the space between the brain and its protective tissues, often caused by a ruptured aneurysm.

C. Transient Ischemic Attack (TIA) — The "Warning Stroke"

A TIA is a temporary blockage with symptoms that resolve completely. It is a critical warning sign. About 1 in 3 people who have a TIA will have a major stroke within a year if left untreated. The risk is highest in the first few days; about 10-15% of people with a TIA will have a major stroke within three months [5]. A TIA is a medical emergency.

2.How to Know You're Having a Stroke: Act B.E. F.A.S.T.

Recognizing the signs and acting quickly can save a life and limit disability. The American Stroke Association promotes the B.E. F.A.S.T. acronym [6]:

B - Balance: Sudden loss of balance or coordination, dizziness.

E - Eyes: Sudden trouble seeing in one or both eyes (blurred, double, or lost vision).

F - Face Drooping: Does one side of the face droop or is it numb? Is a smile uneven?

A - Arm Weakness: Is one arm weak or numb? Does one arm drift downward when both are raised?

S - Speech Difficulty: Is speech slurred or hard to understand? Can they repeat a simple sentence?

T - Time to Call 911: If you see any of these signs, call 911 immediately. Note the time symptoms appeared.

Other Sudden Symptoms to Watch For:

  • Sudden numbness or weakness of the leg, especially on one side.
  • Sudden confusion or trouble understanding.
  • Sudden, severe headache with no known cause.

3.Why Do Strokes Happen? The Risk Factors

Understanding risk factors is the foundation of prevention. Up to 80% of all strokes are preventable [7].

Modifiable Risk Factors (Things You Can Control or Treat)

  • High Blood Pressure (Hypertension): The #1 leading cause of stroke.
  • Smoking: More than doubles the risk of ischemic stroke.
  • Diabetes Mellitus: Increases stroke risk by 1.5 times.
  • High Cholesterol: Contributes to plaque buildup that narrows arteries.
  • Atrial Fibrillation (AFib): Increases stroke risk by nearly five times.
  • Physical Inactivity & Obesity.
  • Poor Diet.

Non-Modifiable Risk Factors (Things You Cannot Change)

  • Age: Risk doubles each decade after age 55.
  • Family History: Higher risk if a close relative has had a stroke.
  • Race/Ethnicity: Significant disparities exist. Black Americans' risk is nearly twice as high as white Americans'. Hispanic and American Indian/Alaska Native populations also face elevated risks [12, 17].
  • Previous Stroke or TIA: Dramatically increases the risk for another.

4.When Do Strokes Happen?

A stroke is an acute event, but it's the result of a long-term process when a risk factor culminates in a vascular event. While it can happen at any time, some research suggests a higher incidence in the morning hours [13]. The key takeaway is that a stroke is not a random event but a predictable consequence of underlying vascular disease.

5.How Can You Prevent a Stroke? Your Action Plan

Prevention is the most powerful tool you have. Focus on these key areas:

  • Manage Your Blood Pressure: Work with your doctor to keep it in a healthy range (generally below 130/80 mmHg [8]).
  • Eat a Brain-Healthy Diet: Adopt a diet like the Mediterranean or DASH diet [14].
  • Engage in Regular Physical Activity: Aim for at least 150 minutes of moderate-intensity activity per week [15].
  • Stop Smoking: This is one of the most significant actions you can take.
  • Control Your Blood Sugar: If you have diabetes, diligent management is crucial.
  • Talk to Your Doctor: Get regular check-ups and discuss medications or a prevention plan.

Emergency Action: What to Do If You Suspect a Stroke

  • Call 911 Immediately. Do not wait.
  • Note the Time. The time symptoms started is critical for treatment options like tPA, which has a 3 to 4.5-hour window [16].
  • Do Not Give Aspirin. It can be deadly in a hemorrhagic stroke. Wait for a medical diagnosis.

View References and Data Sources
  1. Feigin, V. L., et al. (Global Burden of Disease Stroke Collaborators). (2021). Global, regional, and national burden of stroke... *The Lancet Neurology*, 20(10), 795-820.
  2. Saver, J. L. (2006). Time is brain—quantified. *Stroke*, 37(1), 263-266.
  3. American Stroke Association (ASA). (2024). *Types of Stroke*.
  4. An, S. J., Kim, T. J., & Yoon, B. W. (2017). Epidemiology, risk factors, and clinical features of intracerebral hemorrhage: an update. *Journal of stroke*, 19(1), 3.
  5. Centers for Disease Control and Prevention (CDC). (2023). *Transient Ischemic Attack (TIA)*.
  6. American Stroke Association (ASA). (2025). *Stroke Warning Signs and Symptoms*.
  7. O'Donnell, M. J., et al. (INTERSTROKE investigators). (2016). Global and regional effects of potentially modifiable risk factors... *The Lancet*, 388(10046), 761-775.
  8. Whelton, P. K., et al. (2018). 2017 ACC/AHA...Guideline for the Prevention...of High Blood Pressure in Adults. *Hypertension*, 71(6), e13-e115.
  9. U.S. Department of Health and Human Services. (2014). *The Health Consequences of Smoking—50 Years of Progress: A Report of the Surgeon General*.
  10. Centers for Disease Control and Prevention (CDC). (2022). *Diabetes and Your Heart*.
  11. Wolf, P. A., Abbott, R. D., & Kannel, W. B. (1991). Atrial fibrillation as an independent risk factor for stroke... *Stroke*, 22(8), 983-988.
  12. Centers for Disease Control and Prevention (CDC). (2024). *Stroke Facts*.
  13. Manfredini, R., et al. (2018). Circadian rhythms and cardiovascular diseases... *Journal of biological rhythms*, 33(5), 459-472.
  14. Estruch, R., et al. (PREDIMED Study Investigators). (2018). Primary prevention of cardiovascular disease with a Mediterranean diet... *New England Journal of Medicine*, 378(25), e34.
  15. U.S. Department of Health and Human Services. (2018). *Physical Activity Guidelines for Americans, 2nd edition*.
  16. Powers, W. J., et al. (2019). Guidelines for the early management of patients with acute ischemic stroke... *Stroke*, 50(12), e344-e418.
  17. U.S. Department of Health and Human Services Office of Minority Health (OMH). (2024). *Stroke and Health Disparities data*.