This is the VOA Special English Health Report.

A migraine headache can cause disabling pain. People may not feel back to normal for hours or even days.

Migraine headaches are most common among young adults and middle-aged people. In the United States, about eighteen percent of women and six percent of men report having migraines.

People who suffer from migraines can find that different "triggers" in different people may get a headache started. Stress can act as a trigger. So can chocolate in some people.

Many migraine sufferers say hot weather and low barometric pressure can act as triggers. But researchers say they did not have much scientific evidence of that -- until now.

In a new study, a team examined the medical records of seven thousand hospital patients. The patients had visited the emergency room at Beth Israel Deaconess Medical Center in Boston, Massachusetts, because of a headache. More than two thousand of them had been found to have a migraine.

The team then compared those records to weather conditions in the twenty-four hours before the hospital visits. For every increase of five degrees Celsius in air temperature, the patients had a seven and one-half percent higher risk of migraine. Decreases in barometric pressure two to three days before the visit also appeared to trigger headaches, but to a lesser extent.

The researchers found no evidence that air pollution influenced headaches. But they could not rule out the possibility of a smaller effect similar to that seen earlier for strokes.

Kenneth Mukamal of Beth Israel Deaconess and Harvard Medical School led the study, reported in the journal Neurology.

A separate study has found that age, gender and where a person has extra body fat may affect the risk of migraine. It found that overweight people between the ages of twenty and fifty-five may have a higher risk. On average, those who were larger around the middle were more likely to have migraines than those of the same age with smaller waistlines.

The study involved twenty-two thousand people. It was led by Lee Peterlin of Drexel University College of Medicine in Philadelphia, Pennsylvania. She says early results suggest that losing weight in the stomach area may help younger people who experience migraines, especially women. The findings will be presented in a few weeks at the American Academy of Neurology meeting in Seattle, Washington.

And that's the VOA Special English Health Report, written by Caty Weaver. I'm Steve Ember.