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AAOS Now

Published 8/1/2010
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Jennie McKee

Who hurts more—and why?

Sex and gender may affect pain prevalence and mechanisms

“Evidence in the literature suggests that both sex and gender affect clinical pain,” said Linda LeResche, ScD, of the University of Washington.

According to Dr. LeResche, certain conditions are more prevalent in women than men, and pain mechanisms may be different between the sexes. Dr. LeResche spoke at the AAOS/Orthopaedic Research Society/American Bone and Joint Surgeons sponsored research symposium on Musculoskeletal Health Care Disparities.

Studying pain prevalence

“The term ‘sex’ is usually used when talking about biological aspects of identity,” Dr. LeResche said, “whereas ‘gender’ refers to societal influences and how one views oneself and one’s role within society.”

According to Dr. LeResche, age and sex-specific prevalence patterns vary for different pain conditions; however, prevalence rates of the most common chronic pain conditions—including many musculoskeletal pain conditions—are higher among women than men.

“In population-based studies of adults,” she said, “the female-to-male ratios for headache, neck, and shoulder pain average around 1.5 to 1; for orofacial pain conditions, about 2 to 1; for migraine headache, 2.5 to 1; and for fibromyalgia, the ratio is more than 4 to 1.”

Dr. LeResche noted that a 1997 study evaluated the relative prevalence of pain conditions between men and women.

“The list of pain conditions that are more prevalent in women than in men is much longer than the list of conditions that are more common in men,” said Dr. LeResche.

Whether higher rates of pain in women are due to higher rates of onset or to a longer duration of the conditions in women is unclear.

This and other research indicates that women are also more likely than men to experience multiple pain conditions simultaneously, which is associated with higher levels of disability and psychological distress and is a risk factor for onset of new pain conditions. A 1990 study found that individuals with two or more pain conditions were at an elevated risk of an algorithm diagnosis of major depression and that the number of pain conditions reported was a better predictor of major depression than pain severity, pain persistence, or other important measures of pain experience.

Pain mechanisms, societal expectations
Other differences may exist between men and women when it comes to pain mechanisms, said Dr. LeResche, including pain transmission systems, the basic biology of pain, or pain perception (the detection of pain signals).

How patients appraise their pain, biologic changes throughout life, cultural differences in how to view pain, and societal expectations of how to respond to pain can also shape the experience of pain.

Dr. LeResche and colleagues investigated the potential relationship between pain prevalence and puberty.

“Pubertal development is related to increases in the four pain conditions we examined in girls,” she said. “As girls go through puberty, the prevalence rates of back pain, headache, facial pain, and stomach pain all increase.

“The probability of multiple pains and rates of high depression somatic symptoms also increase for girls,” she continued. “For boys, some pains increase while others decrease in prevalence during puberty. The rates of multiple pains, depression, and nonpain somatic symptoms don’t change very much as boys go through puberty.”

A 2003 study on pain across the menstrual cycle found that pain is highest when estrogen is lowest. The worst pain was reported toward the end of the cycle, when estrogen drops.

The role of estrogen is complicated, she said, “but it seems that hormonal factors likely influence women’s experience of facial pain and probably affect other pain conditions. Estrogens may be pain modulators.

“In men, we didn’t find much of a pattern,” she added.

Disability, pain reporting
Sex differences in pain related to disability, said Dr. LeResche, can sometimes be subtle.

“In a large 2003 study that evaluated lost productive time in the U.S. work force due to pain during a 2-week period (including absenteeism and reduced performance), the rates among men and women were similar but the conditions that caused those lost productive time were different,” she said. Women were more likely to lose work time due to headache, while men were more likely to lose work time due to back pain.

A 1994 study that followed people who missed work due to back and other musculoskeletal injuries found that men went back to work early and became disabled again. Women took more time off, noted Dr. LeResche, but were more likely to stay at work after they returned.

“It is a cultural stereotype, borne out by research, that women are more willing to report pain than men; however, it is possible that women seek more health care because they experience greater levels of pain,” she said.

“People who report the most severe pain are those most likely to seek care,” she added. “Although we may find more women than men in clinical care settings, the pain levels of patients in those settings may be very similar.”

Thus, said Dr. LeResche, clinics may not be the best settings in which to examine the question of sex differences in pain.

“According to our data, women are more likely to seek health care for pain, but women are also more likely to experience pain as being severe,” she said. “When you control for the severity of pain, it takes away the difference between the sexes.”

In summary, said Dr. LeResche, “women do seek more health care for pain, but they also report having more pain than men.”

Disclosure information: Dr. LeResche—National Institute of Dental and Craniofacial Research Grant, National Institutes of Health Office of Research on Women’s Health, and Johnson & Johnson.

Jennie McKee is a staff writer for AAOS Now. She can be reached at mckee@aaos.org

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