Studies show that about 795,000 people suffer a new or recurrent stroke each year. About 610,000 of these are first attacks and 185,000 are recurrent attacks. About 137,000 Americans die from stroke each year, according to the Centers for Disease Control and Prevention, making it the third leading cause of death in the United States behind heart disease and cancer.
While the condition is most often associated with older people, young adults under 45, like Biden, are not immune to stroke.
"Many people are shocked and surprised to hear that someone who is 41 has had a stroke," said Dr. Carolyn Brockington, director of the stroke section at St. Luke's-Roosevelt Hospital in New York. "The fact that someone who is 41 has had a stroke is not unheard of."
Indeed, an estimated 10 percent to 15 percent of strokes -- most of them ischemic rather than hemorrhagic -- occur in those under 45, according to Dr. Aneesh Singhal, associate professor of neurology at Harvard Medical School, who practices at Massachusetts General Hospital in Boston.
Even when stroke does not kill, it can cause disabilities such as paralysis, speech and, especially among young people, emotional problems.
Because less is known about this disease among young people, the American Academy of Neurology has just received a grant to study stroke in that population, Singhal said.
"The risk is still very low, but young men and women need to be aware," said Singhal. "Stroke is the leading cause of disability worldwide. It can happen in the young, and one of the real problems is they don't recognize the symptoms and it is often overlooked in the emergency department when they visit."
Just last year, a Wayne State University study revealed that young adults arriving in hospital emergency rooms after a stroke are often misdiagnosed.
Researchers found eight of 57 stroke patients were incorrectly diagnosed with conditions including vertigo, migraine, alcohol intoxication, seizure, an inner ear disorder or other conditions.
The first hours are critical in treatment. In the case of an ischemic stroke, the most common among the young, doctors can administer the clot-busting drug tissue plasminogen activator, or tPA, the only U.S. government-approved treatment for acute stroke. It must be given within three hours of the onset of symptoms to reduce permanent disability.
It is as yet unclear whether Biden received tPA or not. Furlan said the clot-buster is rarely administered to patients experiencing a very mild stroke or whose stroke occurred more than four hours before treatment.
Doctors said that now that Biden appears to be stable, however, the most important course of action is to determine the underlying cause of the stroke.
"If that problem has not been solved, then the risk of having another stroke is certainly present," Brockington said.
"The mild symptoms suggest that full effort will focus on rapidly identifying the cause and intervening to avoid a second event," said Dr. George Newman, chairman of the department of neurosensory sciences at Albert Einstein Medical Center in Philadelphia. "Rehab therapies will follow if needed."