by nate on Thursday, March 12th, 2009 | Health, Life

(CNN) – Headaches, big and small, are among the most common health complaints. Almost 90 percent of women and about 70 percent of men get tension headaches, the Mayo Clinic says. Yet doctors still don’t know much about what causes them.

In a new large-scale study published in the journal Neurology this week, researchers found that higher temperatures and, to a lesser extent, low air pressure, influence severe headaches.

But researchers aren’t sure how temperature influences headaches, and others say that a slew of other factors could be involved in the connection.

“I think it’s more complicated than that,” said Dr. Joel Saper, director of the Michigan Head Pain and Neurological Institute in Ann Arbor, Michigan, who was not involved in the study. Temperature and pressure may be indirect evidence of other causal factors.

The study looked at more than 7,000 patients who had come to the emergency room of Beth Israel Deaconess Medical Center in Boston, Massachusetts, between May 2000 and December 2007, all of whom were discharged with a primary diagnosis of some kind of headache. About 75 percent of these patients were women.

Researchers compared environmental factors such as temperature, air pollution and barometric pressure on the day of the patient’s visit with a day the week before and a day the week after. They found that the risk of severe headache increases about 7.5 percent for each temperature increment of 5 degrees Celsius (about 9 degrees Fahrenheit).

“Fairly consistently, it was warmer on the days that individuals came in than on control days before and afterwards,” said Dr. Kenneth Mukamal, lead author and physician at Beth Israel Deaconess Medical Center.

But as to why temperature is connected to headaches, Mukamal said researchers aren’t sure. The physiological connection is not well understood, he said.

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Tags: doctor, headache, health, hot air, migrain, sickness, weather