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Women are the Hardier Sex...

... When it comes to tolerating pain, new research says

SUNDAY, May 18, 2003 (HealthDayNews) -- She gets a tooth pulled, then drives herself home, makes dinner for four, does the laundry and helps the kids with their homework.

He gets a tooth pulled and his universe slams to a halt, as he waits for the pain to go away.

Caricatures? Sure. But the debate over who can really stand more pain has been one of the more interesting battles of the sexes, spanning generations.

Now, however, new research is bringing that battle into a whole new arena, with strong evidence that the traditionally "weaker" sex may be hardier after all.

"I think men have always secretly suspected that in order to go through childbirth a woman has to be pretty tough. Now we have some new science to back up the idea that women may be better able to cope with pain than men -- at least during certain periods of their life," says Dr. James N. Dillard, author of the The Chronic Pain Solution and an assistant clinical professor at Columbia University College of Physicians and Surgeons in New York City.

The secret weapon? Estrogen. Produced by the ovaries in peak amounts during the reproductive years, and in lesser amounts later in life, the hormone's influence may extend far beyond a woman's reproductive tract. Its powers may reach straight to the pain centers of the brain.

"Although pain is influenced by many factors, it's clear that estrogen plays an important role in the individual response," says Dr. Jon-Kar Zubieta, a neuroscientist at the University of Michigan who has published several studies investigating links between sex hormones and pain.

One way estrogen helps women to cope with pain, he says, is by increasing the availability of endorphins -- brain chemicals that help dampen the pain response.

When estrogen levels are high, there's an increased number of areas in the brain where endorphins can "park." The more "parking places" available, Zubieta says, the more endorphins there are on call, waiting to flood the body with "feel good" chemicals capable of overriding pain signals.

"That's one reason why women can get through the pain of childbirth -- right before they give birth, their estrogen levels are soaring, so their ability to cope with pain is expanded," Zubieta says.

Conversely, studies show this same level of pain protection may drop precipitously the closer a woman gets to menopause, a time when estrogen levels can plummet. That fact, says Dillard, may be one reason why so many women begin to feel more aches and pains as they cross the threshold into mid-life.

"It's not that they are experiencing more things going wrong with their body, as much as they are experiencing a level of pain they were not feeling before," Dillard explains.

As far back as 1993, an animal study published in the journal Pain found that when their ovaries were intact, female rats were far less likely to experience pain than when the ovaries were removed. More recently, studies conducted at the University of Massachusetts revealed that women may have more muscle endurance during exercise than men, thanks again to estrogen, which works to reduce soreness and pain after exertion.

Research also shows testosterone levels make little difference in how male rats experience pain, indicating this hormone may not have the same effect on men as estrogen does on women.

But when it comes to perceiving pain, it's not just hormones that matter. Dillard says social and cultural conditioning matters as well.

"We know that pain pathways go directly into the primitive emotional parts of the brain -- the limbic system. But the degree to which you react to that pain is culturally learned," says Dillard.

What can also matter: Previous experience with pain.

Because women are preconditioned to at least some degree of monthly menstrual pain, not to mention a pretty hefty level of discomfort during childbirth, Dillard suspects they may react with less alarm when other types of pain occur. And this, he says, may make a big difference when it comes time to have that tooth pulled.

"Research has shown that the more upset somebody is about pain -- man or woman -- the more they tend to amplify pain signals and the worse the pain feels," Dillard says. "So, if a woman is used to pain, she will be less alarmed by pain signals, and that leads to better tolerance."

The study of gender-based pain is still in its infancy. And while it's beginning to appear as if women may have some biochemical advantages, ironically, women are also more likely to suffer from pain syndrome illnesses -- conditions such as fibromyalgia, lupus, multiple sclerosis and migraine headaches.

More information

For more information on chronic pain, visit The American Pain Foundation or the National Foundation for the Treatment of Pain.

SOURCES: James N. Dillard, M.D., D.C., C.Ac., assistant clinical professor, Columbia University College of Physicians and Surgeons, clinical adviser, Columbia's Rosenthal Center for Complementary and Alternative Medicine, and director, Complementary Medicine Services, University Pain Center, New York City; Jon-Kar Zubieta, M.D., Ph.D., lead researcher, neuroscientist and director, Psychiatry Division, University of Michigan Depression Center, Ann Arbor
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