Derek Burnett
Derek Burnett is a Contributing Writer at Bottom Line Personal, where he writes frequently on health and wellness. He is also a contributing editor with Reader’s Digest magazine.
Unfortunately, most of us know someone who has suffered a stroke. Each year in the US, 795,000 strokes occur, a rate of one every 40 seconds, and a death from stroke occurs every three minutes and 11 seconds. Despite living in the shadow of this menace, most Americans have only a hazy idea of what a stroke is and what causes it. Knowing more about stroke and its causes can help you lower your risk of experiencing one.
Have you ever wondered whether to stroke is a heart event or a brain event? It’s actually both. The brain and the circulatory system are involved in a stroke. It begins as a problem with the cardiovascular system and, as a downstream effect, the brain is damaged. Despite there being two main types of stroke, in essence, all strokes follow a basic pattern: damage to a blood vessel disrupts the flow of blood to part of the brain.
In an ischemic stroke: An artery carrying blood containing oxygen and nutrients to the brain becomes obstructed by a blood clot. The blood clot may form at a clogged artery leading to the brain (this is known as a thrombus), or it might occur elsewhere in the body, partially dislodge, travel through the bloodstream, and then become lodged in the artery feeding the brain (this is called an embolus). About 87% of all strokes are ischemic.
In a hemorrhagic stroke: A blood vessel in the brain ruptures or begins to leak. The blood from the leak forms a mass known as a hematoma, which causes pressure against the tissue of the brain, choking off its supply of oxygen and nutrients. When a hemorrhagic stroke occurs inside the brain, it’s known as an intracerebral hemorrhage. When the rupture appears between the brain and the skull, it’s called an intracranial hemorrhage.
Whether the stroke is ischemic or hemorrhagic, the effects on the brain can be devastating. The brain is a highly complex and nutrition-hungry organ. When the flow of blood to the brain is disrupted, the damage is immediate, with cells dying at a rate of nearly 2 million per minute. Brain tissue can recover spontaneously if the disruption of blood flow is only brief (this is called a transient ischemic attack, or TIA). But not so if the brain is deprived of oxygen and nutrients for a longer period of time.
When doctors in emergency rooms and stroke centers receive a stroke patient, their immediate goal is to restore blood flow to the brain as quickly as possible. If this treatment is not given within an hour of the first onset of symptoms, the permanent destruction of some brain cells is almost certain. Patients can be left with cognitive deficits, loss of vision, inability to move, speech loss, a diminished ability to recognize their loved ones, and many other long-term impairments.
When an ischemic stroke occurs in one of the two carotid arteries, which run along either side of the neck, damage occurs in the part of the brain known as the cerebral cortex, which is responsible for complex thinking, language, sensory perception, and movement. If the blockage occurs in one of the two vertebral arteries, located on the back of the neck, damage happens to the rear parts of the brain which are home to speaking, breathing, swallowing, and vision. Strokes are not limited to these four main “cervical arteries,” but can also occur in smaller blood vessels in the brain.
Besides causing these types of brain damage that can instantly alter a person’s life, strokes also can kill. About 140,000 Americans every year die from stroke, accounting for one in 20 deaths in the US.
The overwhelming majority of strokes occur as a result of a buildup of plaque inside the blood vessels, causing a thrombus or the rupture or leakage of the vessel. But a few rare conditions occasionally also cause strokes:
Above, we’ve described the very basics of the mechanics of stroke and what’s going on in the body when a stroke occurs. But sometimes when people talk about stroke “causes,” they’re more interested in things like diet, smoking, and other drivers. Experts tend not to refer to such things as “causes,” preferring instead the term “risk factors,” since none of them can be said explicitly to cause someone to have a stroke. Instead, with the addition of each additional risk factor, one’s risk of suffering a stroke increases. Still, of course, a patient could tick every single box for stroke risk without ever experiencing one.
Risk factors are said to be either “modifiable” (within a patient’s control) or “nonmodifiable” (beyond a patient’s control).
Some of the most important non-modifiable risk factors for stroke are:
Age: Unsurprisingly, stroke risk increases the older you get, with two-thirds of strokes occurring in people older than 65. In fact, every 10 years after age 55, stroke risk more than doubles.
Sex: More strokes happen to women than to men. That may be because women generally live longer, or it could have to do with hormone therapy or with changes brought about by reproductive issues including miscarriage, pre-eclampsia, and complicated pregnancies.
Race: Likely at least in part due to the stresses and inequalities of systemic racism, young and middle-aged Black patients face a stroke risk four times higher than that of whites, and the rate for Hispanics is double that of whites.
Genetics: Scientists are still sorting out the genetics of stroke risk, but there are clear patterns when it comes to family history. If an immediate family member has had a stroke, your risk goes up by nearly a third. If one of your parents had a stroke before age 65, your risk triples. Not all family-history risk is genetic, however, since you may have picked up dietary, exercise, smoking, and other habits from your family.
Prior stroke: Almost a quarter of all strokes occur in patients who have already had one or more strokes.
Some of the most important modifiable risk factors for stroke are:
There are some risk factors that occupy a gray area between modifiable and non-modifiable. These are medical conditions that you obviously haven’t chosen, but whose effect on stroke risk can be diminished by treating or managing them closely. They include:
Knowing your risk can allow you the opportunity to reduce that risk with education, a healthy diet, regular exercise, quality sleep and avoiding smoking, alcohol, and drugs.
