Younger adults who suffered a stroke were often smokers or had abused drugs or alcohol, according to a U.S. study that looked at over 1,000 patients.
Strokes are often thought of as a condition of the elderly, but researchers said long-term changes in the heart, arteries or and blood as a result of drug abuse or heavy drinking may put users at higher-than-average risk earlier in life.
"Substance abuse is common in young adults experiencing a stroke," wrote lead researcher Brett Kissela from the University of Cincinnati in the journal Stroke.
"Patients aged younger than 55 years who experience a stroke should be routinely screened and counseled regarding substance abuse."
It's also possible that some drugs, particularly cocaine and methamphetamines, may trigger a stroke more immediately, according to S. Andrew Josephson, a neurologist from the University of California, San Francisco, who has studied drug use and stroke but was not involved in the study.
"We know that even with vascular risk factors that are prevalent - smoking, high blood pressure... most people still don't have a stroke until they're older," he added.
"When a young person has a stroke, it is probably much more likely that the cause of their stroke is something other than traditional risk factors."
According to the U.S. Centers for Disease Control and Prevention, close to 800,000 people in the United States have a stroke every year, and they are the most common cause of serious long-term disability. One study of 2007 data found that almost five percent of people who had a stroke that year were between ages 18 and 44.
The current study involved people from Greater Cincinnati and Northern Kentucky who'd had a stroke before they hit 55.
The researchers reviewed medical charts for blood or urine test results of other records of substance abuse for close to 1,200 stroke patients.
In 2005, the most recent year covered, just over half of young adults who suffered a stroke were smokers at the time, and one in five used illicit drugs, including marijuana and cocaine. Thirteen percent of people had used drugs or alcohol within 24 hours of their stoke.
"The rate of substance abuse, particularly illicit drug abuse, is almost certainly an underestimate because toxicology screens were not obtained on all patients," said Steven Kittner, a professor of neurology at the University of Maryland School of Medicine in Baltimore who also wasn't part of the research.
The rate of smoking, drug use and alcohol abuse - defined as three or more drinks per day - seemed to increase among stroke patients between the mid-1990s and the mid-2000s.
But Kissela and his team said they can't be sure whether more people were actually using those substances or doctors were just getting better at testing for and recording drug abuse.
The study also can't prove that patients' drug or alcohol use directly contributed to their strokes. It's possible, for example, that people who abuse drugs also see their doctors less often or engage in other risky behaviors that increase the chance of strokes, Josephson explained.
He added that the study emphasizes the need to learn and quickly recognizing the signs of strokes, even in young people, since some treatments can only be used in a short window of opportunity after the stroke.