MONDAY, April 14 (HealthDay News) -- People with high blood pressure are less likely to have headaches than those with normal blood pressure, a new study suggests.

But one headache expert cautions that the new research does not mean those with hypertension should not get treated or stop taking their blood pressure medications.

The stiff arteries that are associated with the high blood pressure -- making people less sensitive to pain -- may be the reason why those with hypertension seem to suffer fewer headaches, including migraines, according to the new research, published in the April 15 issue of Neurology.

At this point, the results are more of scientific interest for researchers than for consumers.

"This is an epidemiological study, and the results cannot be used on an individual level," said study author Dr. Erling Tronvik, a physician with the Norwegian National Headache Center at Trondheim University Hospital in Trondheim, Norway.

"The results may, however, be used to try to explain some mechanisms involved in headache and migraine," he said.

Tronvik's team set out to better understand the relationship between blood pressure and headache. In years past, headache was thought, mistakenly, to be more common among those with high blood pressure. Later research debunked that view.

Tronvik's team used data from two large studies, one conducted from 1984 to 1986 and the other from 1995 to 1997.

The first focused on blood pressure and diabetes, and included data from more than 77,000 people. The second evaluated data from more than 51,000 men and women who had their blood pressure measured and completed a questionnaire on headache. They also gave information on whether they took blood pressure medications, which are sometimes used to treat migraines.

The findings: Those with higher systolic blood pressure were up to 40 percent less likely to have headaches compared to those with healthier blood pressures. Systolic pressure is the top number of a reading, representing the maximum pressure when the heart contracts.

The researchers also looked at another measurement, called the pulse pressure, or the change in blood pressure when the heart contracts. It's computed by subtracting the diastolic reading (bottom number) from the top.

Those with higher pulse pressure had up to a 50 percent reduction in the number of headaches.

Further research may hold clues that would help headache sufferers. "We would like to examine whether there are any common pathways in the autonomic nervous system with regard to blood pressure regulation and headache, and whether it also can be demonstrated on an individual level," Tronvik said.

The results make sense to another expert, Dr. Nabih Ramadan, a staff physician at the Diamond Headache Clinic, in Chicago.

"The higher the pulse pressure," he explained, "the stiffer the blood vessel is going to be. The stiffer the blood vessel, the less likely the nerve endings are activated. The less likely the nerve endings are activated, the less likely you will get headache."

The study has weaknesses, Ramadan said. Among them: Pulse pressure is a very crude measurement and, as the authors noted, it was unknown whether participants were on blood pressure medicines for high blood pressure or for headaches.

Ramadan emphasized that those with high blood pressure need to be treated to bring the level down.

More information

To learn more about migraine, visit the National Headache Foundation.

SOURCES: Erling Tronvik, M.D., researcher, Norwegian National Headache Center, Trondheim University Hospital, Trondheim, Norway; Nabih Ramadan, M.D., board member, National Headache Foundation, and staff physician, Diamond Headache Clinic, Chicago; April 15, 2008, Neurology

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