People have been blaming the weather for their aches and pains for centuries. Some claim they can forecast the weather in their hips or knees. Other scoff. Now, science suggests some of these people may be on to something.

Researchers at Beth Israel Deaconess Medical Center, in Boston, say higher temperatures and low barometric pressure do indeed seem to set off migraine, tension and other severe headaches. Their results appear in the March 10 issue of the journal Neurology. (That's Oakland Athletics player Rickey Henderson, above, coping with a migraine that took him out of a game against the Orioles in July 1994.)

In what they describe as the first large-scale investigation of this weather lore, the Boston investigators looked at the medical records of more than 7,000 patients who visited the emergency room at the medical center between May 2000 and December 2007, and who were discharged with diagnoses of migraine, tension or unspecified headaches.

Then they looked at measurements of average air temperature, barometric pressure, humidity - as well as several measures of air pollution prior to those hospital visits, again on the same days of the week before or after their hospital visits during the same calendar month.

The idea that environmental factors can trigger migraine headaches is not new. Certain foods - such as aged wine and cheese - alcohol, stress and hormonal changes have long been recognized as headache "triggers." And some patients have long associated their maladies with changes in the weather.

"But none of these [weather factors] have been consistently verified. We wanted to find out if we could verify this clinical folklore. We also wanted to determine whether air pollutants trigger headaches, much as they have been found to trigger strokes," said Dr. Kenneth Mukamal, the study's lead author.

His findings revealed no significant impact from air pollutants, or from humidity. But higher average air temperatures in the 24 hours before these patients sought hospital care was the single factor most closely correlated with the headaches. Headache patients in the study had a 7.5 percent higher risk of suffering a severe headache for each increase of 9 degrees Fahrenheit.

That isn't a large increased risk compared to exposure to certain foods, or other potential migraine "triggers," and it may not be an important consideration in the way these patients are treated, Mukamal acknowledges in the paper. But the fact that everyone is exposed to the weather, while only a fraction would be exposed to other triggers, the public health impact of higher temperatures would likely be much greater. 

Also significant, but less so, were changes in air pressure. Changes in pressure didn't seem to be a factor, but lower barometric pressures 48 to 72 hours prior to the ER visits also seemed to correlate best with the severe headache symptoms that followed.

The study had some limitations, the authors agreed. They relied on regional weather data, not readings for each patient, so their personal exposures were not recorded. They also knew when the patients appeared at the hospital, but could not say when the patients'  headaches began. 

Nevertheless, "these findings help tell us that the environment around us does affect our health and, in terms of headaches, may be impacting many, many people on a daily basis," Mukamal said.

Still unclear is how this happens. "[Higher] temperature has a host of physiological effects, including lower blood pressure," Mukamal said in an email message. "How those lead to headache is uncertain, but we don't understand the full mechanisms behind headaches at this point, so hopefully this will point us in new directions."