THURSDAY, July 28 (HealthDay News) -- In the three months after a traumatic brain injury, the risk of stroke may increase 10-fold, Taiwanese researchers report.

"Traumatic brain injury has not been included among the usual stroke risk factors in the past," said Dr. Ralph Sacco, president of the American Heart Association/American Stroke Association, who is familiar with the study. "The mechanism is still not clear, but deserves further investigation."

Sacco, also chairman of the department of neurology at the University of Miami Miller School of Medicine, said it's known that patients with traumatic brain injury can have other complications, such as ruptured or torn arteries, cardiac injuries or blood clotting disturbances, that increase the risk of stroke.

In the United States, about one in 53 people has a traumatic brain injury each year, according to the U.S. Centers for Disease Control and Prevention. Because impairment following traumatic brain injury may be invisible, the researchers said the condition is sometimes described as a silent epidemic.

For the study, published in the July 28 online edition of Stroke, a team led by Herng-Ching Lin, a professor at Taipei Medical University, collected data on 23,199 people who suffered a traumatic brain injury between 2001 and 2003. They compared these patients with 69,597 patients without traumatic brain injury.

Among those with a traumatic brain injury, 2.91 percent had a stroke within the first three months after the injury, compared with 0.30 percent of those who had not experienced traumatic brain injury, the researchers found. That's a 10-fold increase, Lin's group noted.

Over time, however, the risk of stroke diminished among those with traumatic brain injuries, the researchers said. After a year, the risk was 4.6 times greater, and after five years it was 2.3 times greater for these patients than for people without traumatic brain injury.

A fractured skull significantly boosted stroke risk. Within three months of a skull fracture, the risk for stroke was 20 times higher than for brain-injured patients with no skull fracture, the researchers found.

Also, patients with a traumatic brain injury were at greater risk for bleeding in the brain, compared with people who had not experienced traumatic brain injury.

The brain-injured patients also were more likely to have high blood pressure, diabetes, coronary heart disease, atrial fibrillation and heart failure than non-traumatic brain injury patients, Lin's group said.

"Stroke is the most serious and disabling neurological disorder worldwide," Lin said in a journal news release. "Our study leads the way in identifying stroke as an additional neurological problem that may arise following traumatic brain injury."

Lin said early neuroimaging examinations, such as MRI, and intensive monitoring should be standard in the first few months and years after a traumatic brain injury.

Commenting on the study, Dr. Larry B. Goldstein, director of the Duke University Stroke Center in Durham, N.C., said the study could not adjust for major risk factors for stroke or their treatment, or prove a causal connection between traumatic brain injury and stroke.

"Those that have had traumatic brain injury may differ from those who do not, and it may be these other differences that lead to stroke rather than the trauma itself," Goldstein said.

"Even minor trauma, however, can sometimes cause a tear in an artery that can compromise blood flow to the brain and cause a stroke," he said.

More information

For more information on stroke, visit the U.S. National Library of Medicine.