THURSDAY, April 1, 2010 (HealthDay News) -- Young adults who have an overactive thyroid face a much greater risk of stroke than people without the condition, Taiwanese researchers report.
"This is a well-controlled analysis, and patients with hyperthyroidism should receive prompt treatment to prevent these complications," Dr. Majaz Moonis, director of stroke services at the University of Massachusetts in Worcester.
Whether hyperthyroidism causes stroke or is a marker for other risk factors isn't known, but Moonis said the study results are not surprising. "Patients with hyperthyroidism have greater hypertension and atrial fibrillation, which is well-documented," he said.
For the study, published online April 1 in Stroke, a team led by Herng-Ching Lin from the School of Health Care Administration in the College of Medicine at Taipei Medical University collected data on 3,176 young adults with hyperthyroidism. They compared these people with 25,408 similar people who did not have hyperthyroidism. The average age was 32.
The researchers followed the patients for five years. During that time, 198 people (0.7 percent) suffered a stroke, including 31 (1 percent) of patients with hyperthyroidism and 167 (0.6 percent) without it, the researchers found.
After taking into account factors such as age, sex, income, environment, high blood pressure, diabetes, an irregular heart rhythm called atrial fibrillation, high cholesterol, coronary heart disease and whether they were taking medication to treat heart rhythm problems, the risk of having a stroke was 44 percent higher for patients with hyperthyroidism than for those without it, Lin's team found.
This is the first study to document a link between stroke and overactive thyroid in people under 45, he said.
"Our study shows an association between hyperthyroidism and the risk of subsequent ischemic stroke [stroke caused by a blood clot] in young adults," Lin said in a statement. "A more thorough evaluation in future studies may help elucidate the causes of stroke in this age group. Our results indicate a need for thyroid function testing and detection of hyperthyroidism in surveys to identify the causes of ischemic stroke in young people."
Lin said up to 2 percent of the world's population have an overactive thyroid, which revs up the metabolism and causes sweating, weight loss, diarrhea and nervousness.
In older adults, hyperthyroidism is associated with atrial fibrillation, which can lead to stroke or sudden cardiac death. However, this relationship has not been documented in younger adults, Lin said.
Another expert, Dr. Larry B. Goldstein, director of the Duke University Stroke Center, doesn't think this study shows a causal relationship between hyperthyroidism and stroke.
"The question is, is this real and what is the potential mechanism?" he said. "The overall risk appears to be relatively small. There would need to be 250 people with hyperthyroidism before one would have a stroke."
Treating the hyperthyroidism would probably eliminate the risk factors associated with the risk of a stroke, Goldstein said.
To learn more about stroke, visit the Stroke Association.