THURSDAY, June 22 (HealthDay News) -- An unexpectedly high number of troops serving in Iraq are suffering from migraine headaches, researchers report.

The debilitating headaches are affecting more than one-third of U.S. soldiers in Iraq, or about twice that in the general U.S. population, according to a study being presented at the annual American Headache Society (AHS) meeting now underway in Los Angeles.

Factors like heat, stress and exhaustion can all raise risks for migraine, experts say, and could be to blame for the high incidence reported.

"Migraines are common among U.S. military personnel in a combat zone -- up to 37 percent of those in Iraq," said study lead author Dr. Brett Theeler, a neurology resident at Madigan Army Medical Center, Fort Lewis, Washington, at a Thursday news conference. "This greatly exceeds the prevalence expected for the same age and gender."

These migraines were also underdiagnosed and undertreated and significantly impaired the soldiers' ability to do their jobs, experts added.

Migraines are particularly debilitating headaches that plague about 28 million Americans. The condition costs the economy more than $13 billion each year in lost work.

"The World Health Organization ranked migraine attacks as one of the most disabling conditions known to mankind," said Dr. Stephen Silberstein, director of the Jefferson Headache Center at Thomas Jefferson University Hospital in Philadelphia, at the same news conference. "It is equivalent to acute psychosis and quadriplegia. People have attacks all the time, and they have significant disability."

Many factors that can contribute to migraines are present in Iraq, Theeler said.

"We hypothesized that migraines would be common among soldiers in Iraq because they can be linked with physical exhaustion, dehydration, abnormal meal patterns, exposure to fumes and extreme heat, among other things," he said.

Theeler's study is the first to look at migraines among active-duty soldiers, although there have been case reports and articles from previous conflicts.

Headache questionnaires were completed by 2,697 U.S. soldiers from Fort Lewis, Washington. The questionnaires included questions about symptoms experienced during the last three months of deployment.

Nineteen percent of the soldiers surveyed reported headaches meeting the criteria for migraine, 18 percent reported headaches meeting the criteria for probably migraine and 11 percent reported having non-migraine headaches. Only 5 percent had previously been diagnosed with migraine.

The majority of the respondents (95 percent) were men.

Soldiers with definite migraines had an average of 3.5 attacks every month, lasting an average of five hours per attack, and made a total of 477 sick call visits, Theeler said. Only 2 percent of these soldiers were using one of the family of triptan medications, deemed the most effective for this condition.

Although no one knows precisely why the incidence of migraine would be elevated in this group, the reason probably has to do with different stressors, the authors said.

The researchers contacted the soldiers again three months after they had returned home. "The migraines tended to persist after they got home and, in many cases, became more severe," Theeler said.

Health officials are now trying to intervene before men and women are deployed. "We have started educating soldiers about migraine headaches and are developing a migraine-screening program to identify people prior to deployment, so that appropriate treatments can be prescribed," Theeler said.

More information

For more on migraines, visit the National Migraine Association.