By Christine Penko
GAINESVILLE, Fla.---Women with chronic pain report slightly higher levels of pain than their male counterparts, but the difference may be as much the result of how society teaches men to handle discomfort as it is a consequence of biology, University of Florida researchers report in the December issue of The Journal of Clinical Psychology in Medical Settings.
"Our study is one of the first to look at sex differences in pain as part of some disease process, and what we find is a very small difference between the pain reported by men and women," said Michael E. Robinson director of the UF Pain Research Laboratory and an associate professor in the College of Health Professions' department of clinical and health psychology. "On the average, the female chronic pain patients reported 3 to 10 percent more pain."
Chronic pain, which partially or totally disables 50 million Americans, is a major public health problem in the United States, according to the American Pain Society. Forty-five percent of all Americans seek care for persistent pain at some point in their lives. Annual medical costs, lost income and productivity, workers' compensation and legal costs associated with chronic pain are estimated at $50 billion.
The UF research involving chronic pain patients is part of a series of studies at the university focusing on how men and women respond to pain.
"There is a definite need to better understand all the neurophysiological and psychosocial factors in how we experience pain," said Roger Fillingim, an assistant professor in the department of psychology at the University of Alabama at Birmingham who has conducted extensive pain research. "One way to do this is by comparing groups of people, such as men and women or older and younger people, to see if there are any differences in pain perception and pursue the reasons why differences exist."
There is tremendous potential for this type of research to affect how pain is treated, Fillingim said. Evidence now suggests men and women respond differently to certain drugs, including analgesics used to treat pain. Assumptions about analgesic dosages are based on studies with men, but learning about sex differences in pain may require rethinking how much medication to give people based on their sex, he said.
The three-year UF study of chronic pain patients, conducted at three university-affiliated tertiary-care clinics, involved 1,700 adults with chronic pain in various areas, such as the back or face. The participants were at least 18 years old, with an average age in the mid-40s. The ratio of men to women was nearly even. When the patients came to the clinics for regular appointments, clinical psychologists measured and evaluated their pain with standardized pain questionnaires.
The small differences in pain reported by men and women in the clinics were considerably lower than those reported in a laboratory. In an earlier UF study that reviewed other studies of sex differences in experimental pain perception, women reported approximately 20 percent more discomfort than men. Researchers attribute the stronger sex differences in those studies to the presence of gender role expectations in the laboratory.
"Men in our society are taught to be tough when it comes to pain, and they're supposed to be able to take it," Robinson said. "In chronic pain patients, however, the men are not concerned with being tough and living up to the role of the average male. Pain is the overriding factor and they want relief. It's different in the lab because they know the pain is temporary. In that situation, there is a response cost to males if they admit something hurts."
In one test, for example, study participants placed their hands in ice water for as long as they could stand the cold. Men tended to respond competitively and left their hands in the water longer. Women typically removed their hands sooner because they did not feel pressure to prove their toughness and endure unnecessary pain, Robinson said.
Other methods frequently used to measure experimental pain include heat and pressure stimuli and back extensions.
"We really believe that the minor sex differences in pain come from physiological factors and the larger differences result from social learning," said Robinson. "This could carry long-term implications for how we teach male and female children in this culture to respond to pain."
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