Women have a higher pain threshold

How we experience pain depends on our sex. Plus: Why female redheads are different.

For years, researchers assumed that women have a higher pain threshold and are less sensitive to pain than men. After all, men don't have to pass a head the circumference of a large grapefruit through an opening that starts at the diameter of a Cheerio as women do to give birth.

But recent research has called into question the assumption that women have greater pain tolerance. Science is providing new insights into pain relief, anesthesia and, oddly enough, redheads.

Jeffrey Mogil, Ph.D., is professor of pain studies at McGill University in Montreal, Canada. He explains that while not all studies have found sex differences, those which have all point in the same direction that contradicts conventional wisdom. "Females are more sensitive to pain, less tolerant and more able to discriminate different levels of pain than males," he says. This is true in studies of both humans and animals.

Women are also much more likely to suffer from chronic pain conditions than men. Researchers originally suspected that this was primarily due to the fact that they are more likely to seek medical care in general. But while women do indeed seek more care, they're also genuinely more likely to develop painful conditions like fibromyalgia, rheumatoid arthritis and migraines. For example, 80 to 90 percent of people with fibromyalgia are women, according to the National Institute of Arthritis and Musculoskeletal and Skin Diseases.

Pregnancy actually is the exception to the rule. While pregnant, women do become progressively less sensitive to pain as they get closer to giving birth.  Natural painkillers like endorphins are elevated during pregnancy and labor, helping fight pain.

Says Mogil, studies show "there is [pregnancy-related pain relief] in both rats and humans," but, he adds, very little research has been done on this in recent decades. He also notes that it's not very effective in humans, given the amount of pain that most women still suffer.

Qualitative differences

Scientists have discovered that women's experience of pain may be not only quantitatively different, but qualitatively as well. And here's where the redheads come in.

Anesthesiologists had long reported that redheads tended to need more anesthesia than others. But until 2002, no studies had been presented on the subject. Up until that point, it could have just been a clinical myth prompted by a few memorable anesthesia-resistant Gingers. However, when a research group in Louisville, Ky., studied the phenomenon, they found that redheads did indeed need larger doses of a common anesthetic—about 20 percent higher, on average—to blunt the pain from electrical shock.

This finding turned out to only be part of the story.

In research conducted by Mogil's group on opioid medications, only redheaded women were different from others in the way these drugs relieved their pain. Plus they needed less opioid painkillers than brunettes or blondes. Male redheads were the same as everyone else.


http://health.msn.com/health-topics/pain-management/articlepage.aspx?cp-documentid=100218149&page=2