Overactive Thyroid May Raise Early Stroke Risk

44% Increase Seen in Younger Thyroid Patients

By Salynn Boyles
WebMD Health News

Reviewed By Laura J. Martin, MD

April 1, 2010 -- Younger adults with overactive thyroids appear to have an increased risk for early stroke, new research finds.

Having the condition known as hyperthyroidism before the age of 45 was associated with a 44% increased risk of stroke in the study conducted by investigators with Taiwan's Taipei Medical University.

Strokes are uncommon, but on the rise, in adults in their 20s, 30s, and 40s.

One recent study showed a dramatic increase in strokes among U.S. adults at the

Between the mid-1990s and 2005, the stroke rate increased from 4.5% to 7.3% in adults between the ages of 20 and 45, according to the data from Ohio and Kentucky.

As many as a third of strokes in younger adults have no obvious cause, Taipei Medical University's Herng-Ching Lin, PhD, tells WebMD.

Hyperthyroidism is a risk factor for the heart-rhythm disorder atrial fibrillation in older adults, and atrial fibrillation is, in turn, a risk factor for stroke.

While overactive thyroid is suspected of contributing to stroke risk in the elderly, its potential role in strokes occurring in younger adults had not been studied until now, Lin says.

Overactive Thyroid and Stroke

Lin and colleagues compared outcomes among Taiwanese adults under age 45 with and without hyperthyroid disease.

A total of 3,176 patients with a new diagnosis of overactive thyroid and 25,408 people without thyroid disease were included in the study.

During five years of observation, 198 people (0.7%) had strokes, including 167 (0.6%) of those without thyroid disease and 31 (1%) of those with thyroid disease.

After adjusting for known risk factors for stroke, including older age, blood pressure, diabetes, and history of atrial fibrillation, the researchers concluded that having an overactive thyroid was associated with a 44% increased risk for ischemic stroke, which is stroke cause by blocked arteries.

“This study is important because hyperthyroidism has not been considered a potential risk factor for stroke and there are up to a third of young ischemic stroke patients without a determined cause,” Lin says.

Reducing the Risk of Stroke

Lin adds that more research is needed to confirm the association.

In the meantime, he says young adults with hyperthyroidism should be vigilant about monitoring their thyroid status and they should do all they can to reduce their modifiable risk factors for heart attack and stroke, such as maintaining a healthy weight, remaining active, and avoiding smoking.

While Lin and colleagues suggest that young stroke patients be routinely tested for hyperthyroidism, Wayne State University assistant professor of neurology Brian Silver, MD, says the recommendation may be premature.

Silver is a spokesman for the American Heart Association.

“At this point, we don't know if treating the thyroid would have any impact on stroke risk,” he tells WebMD. “What we do know is that strokes are becoming more common among young adults and we believe this is mainly due to increases in obesity, hypertension, and diabetes. For young patients, the critical thing would be to address these established risk factors.”

SOURCES:

Sheu, J.J, Stroke: Journal of the American Heart Association, May 2010; online edition.

Herng-Ching Lin, PhD, School of Health Care Administration, College of Medicine, Taipei Medical University,Taiwan.

Brian Silver, MD, senior staff neurologist, Henry Ford Hospital; assistant professor of neurology, Wayne State University School of Medicine, Detroit; spokesman, American Heart Association.

News release, American Heart Association.

American Heart Association: "Stroke Incidence Rising Among Younger Adults, Decreasing Among Elderly."

© 2010 WebMD, LLC. All rights reserved.