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Vol. LX, No. 22
October 31, 2008

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Sex and Gender Research: Pain
ORWH Seminar Looks at a Sensitive Issue

Three perspectives on the response of the gastrointestinal tract to pain and stress were presented in the recent Women’s Health Seminar Series: Sex and Gender Research—Pain.

Dr. Lin Chang, professor of medicine at UCLA’s David Geffen School of Medicine, discussed sex differences in visceral pain in irritable bowel syndrome (IBS). “In the United States, about 7 to 10 percent of individuals meet criteria for IBS,” she said. “What you should know is that the majority of individuals that meet criteria for IBS don’t seek health care.”

Chang said the prevalence of IBS according to age peaks around 30 to 40, then decreases after 50. IBS is also more likely to occur in women than in men; and women are more likely to be diagnosed and treated. When presenting with IBS, women are more likely to experience symptoms of abdominal pain, bloating with distension, urinary urgency, muscle stiffness and altered taste or smell. Chang noted that fluctuation in ovarian hormones also adversely affects IBS symptoms for women.

In addition, Chang said, stress plays a role. “It’s been shown that chronic stress may be associated with increased vulnerability for individuals at risk for developing chronic pain disorders such as IBS,” she said. “The number one chronic stress is a change in the role in your life.” She also noted that a greater proportion of IBS patients have reported childhood, physical, verbal or sexual abuse.

Dr. Jennifer Labus, adjunct assistant professor of psychiatry and biobehavioral sciences at UCLA, talked about sex differences in brain responses in IBS. She described a study where patients were placed in a scanner and had their brains monitored while experiencing experimental stimuli, which caused different active areas in the brain to light up. “Research has shown response to IBS symptom-like stressors suggests that females may show a greater engagement of known emotional-arousal regions,” she said.

Labus noted significant sex differences were demonstrated in the connectivity of brain regions. “There are differences in visceral pain in autonomic functioning between men and women with IBS,” she said. In particular, women experienced enhanced responsiveness when expecting increased stress or pain. She said results of the study were “consistent with reduced feedback inhibition of an emotional-arousal circuit in women with IBS.”

Dr. Muriel Larauche, postdoctoral fellow at the Center for Neurobiology of Stress, spoke on sex differences in responses of the gastrointestinal tract to stress and the implication of corticotropin releasing factor (CRF)-signaling pathways.

She said women have a 50 percent higher rate of CRF, a hormone involved in the stress response, in the colon than men. This higher rate of CRF can have an increased effect on IBS. “Increased expression of CRF in response to stress is much higher in females, by 70 percent, compared to males, who have only a 40 percent increase,” Larauche said.

She also said reactions in the gastrointestinal tract and colon are modulated by sex steroids, such as estrogen. This finding may have implications for the treatment of IBS in women. NIHRecord Icon

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