The Significance of Gender
By Janis Kelly

Fibromyalgia occurs at different rates in women and men, and it manifests differently when it appears. Research with men has lagged behind research with women because fewer diagnosed FM patients are male, but experts report that a clearer picture of the disease is emerging from recent studies. The latest findings suggest that different treatment approaches may be needed for men and women.

Different Pains, Different Gains
Fibromyalgia researcher Muhammad B Yunus, MD, says that men have fewer tender points, are less likely to say that they hurt all over, have less fatigue, and exhibit fewer symptoms. Men are also less likely to have overlapping conditions such as irritable bowel syndrome.

Conversely, men and women have similar pain severity, anxiety, stress, and depression.

“Men tend to have less tenderness with pressure, for example, if the tender point is palpated or bumps into something. Men also tend to have less pain in general,” says Yunus. “Women with Fm are literally more tender than men, but men seem to have more sleep problems.”
 
A study of 536 Fm patients (469 women, 67 men) by Yunus and colleagues at the University of Illinois Medical College, Peoria, showed that the number of tender points is the most powerful discriminator between male and female FM patients. Women are 10 times more likely to have 11 or more tender points than men. However, this does not translate into less disability for men. “Functional status, as measured by the Health Assessment Questionnaire, stiffness, and pain were similar and men and women,” says Yunus. 

A number of social factors such as religious belief, ethnic background, and gender stereotyping by society also influence how pain is felt. “In keeping with social expectation, boys demonstrate less fear of pain and use fewer affective words than girls to express their perception of pain,” says Yunus. “These childhood traits persist into adulthood. Men tend to articulate less pain than women, lest they appear ‘feminine.’”

Some of these social effects were illustrated in a study of men with FM by Dr. Margareta Paulson and colleagues in Sweden. Paulson writes: “Striving to live life required achieving balance during both calm and difficult phases of the illness—struggling for a tolerable existence.”

Five major themes emerged from the Swedish study. Men reported:

• Feeling afraid of being seen as a whine
• Feeling like a guinea pig
• Feeling hopeful
• Feeling neglected
• Feeling no recovery

Paulson says that a man with FM tends to endure a lot of pain before seeking medical help, at which point he may have difficulty finding someone who will listen and take his pain seriously. Men also reported feeling like guinea pigs because of the need for multiple examinations and numerous treatments. Some felt hopeful after referral to a specialized pain or fibromyalgia clinic. Others felt neglected and looked upon by medical professionals as uninteresting cases. Finally, men had to come to terms with the chronic, complex nature of FM and the fact that pain relief does not equal a cure.

Pain Responses and Treatments
Men in general have higher pain thresholds, a lower ability to tell the difference between painful sensations, and higher pain tolerance than women. Men and women not only have different levels of pain sensitivity, their brains and nervous systems also have different ways of responding to pain. Some of these differences may set up women for greater susceptibility to FM.

“One possibility is that enhanced pain sensitivity due to dysfunction of some endogenous pain modulatory systems predisposes people to FM. Perhaps this type of altered pain modulation is more common or more easily produced in women, which leads to the female predominance of FM. Whether the altered pain processing is the same in men and women with FM has not been determined. This is an important question, and it will let us know whether treatment should differ for women and men,” says pain expert Roger B Fillingim, PhD, of the University of Florida College of Dentistry in Gainesville.

Yunus says this means that some pain stimuli may feel more painful to women than to men with FM. “we don’t know if men and women respond the same way to many stimuli. A comparative study is hard to do because it is hard to find enough men with FM to collect statistically significant data.”

“If psychosocial variables, such as coping, influence pain responses, then the efficacy of cognitive-behavioral therapy may differ for women and men,” says Fillingim. “It also appears that certain classes of opioid analgesics are more effective for women than for men. It is conceivable that pain treatment would be tailored based on sex differences.” He notes that the pain-reducing capacity of tactics such as learned coping strategies can be blocked by the opioid-blocking drug Naloxone. “The sex-related influences of these variables may represent evidence that endogenous opioid activation differs for women versus men,” Fillingim adds. For example, a low dose of Nalbuphine, which acts mainly at kappa opioid receptors, relieves pain in women but has no effect on pain in men—or may actually increase it.

The kappa receptor is not the only one to act differently in men and women. The mu opioid receptor, which is involved in “turning down” the feeling of pain, also behaves differently. In men, sustained pain increases the activity of mu receptors. I women, the same type of pain reduces activity of mu receptors in a part of the brain where such receptors would be expected to provide pain relief. This may increase the feeling of pain the next time it is encountered. According to Fillingim, “This study is the most direct evidence to date in humans of a sex difference in endogenous pain modulation.”

The Bigger Picture
As the different results with pain-relieving drugs suggest, it now appears that there are differences in how men and women feel and cope with pain. Another of these differences is in the body’s own (endogenous) pain-stopping methods. One odd fact about the nervous system is that one pain can sometimes lessen or block out another. This si why painful “counterirritant” substances such as capsaicin are sometimes effective pain relievers. This type of “stress-induced anesthetizing” (SIA) reduces certain types of experimental pain in normal males and females, but not in patients with FM.

“Most of the information regarding sex differences in SIA and other forms of endogenous pain reduction comes from studies of non-human animals and may not translate to humans. Tht being said, most studies of SIA find that male animals experience greater analgesia after stress, and other studies show that the neurochemistry underlying SIA seems to be different between sexes,” Fillingim says.

How we hurt and how we deal with it are also partly determined by our family history—and that history affects men and women differently. Women (but not men) who have more family members with two or more types of pain are more likely to report pain themselves, and to have a greater sensitivity to pain tests in laboratory situations. One reason may be increased levels of “hypervigilance,” which means paying too much attention to one’s symptoms and internal sensations. People who are hypervigilant are less able to tolerate pain.

Women with high rates of chronic pain among their close family members are also more likely to be hypervigialant, to feel pain in more places, to feel more severe pain, and to report worse general health than women whose family members do not have such pain histories. Family history did not change any of these pain factors I men. “A family history of pain is associated with increases pain complaints and enhanced experimental pain sensitivity in females, but not in males,” Fillingim says.

Social learning may play a part here, because we learn many of our ways of dealing with pain by watching how our parents and other family members do so. Women are generally better at decoding non-verbal signals than males and so may be more likely to notice when people are in pain. “Females’ greater awareness of non-verbal clues may render them more susceptible to the social learning influences created by exposure to family members with pain,” Fillingim writes. That is, they may recognize more role models for how to notice and express pain.

Animal studies have suggested that there might be a sex-linked genetic component to pain differences. Women, in general, report more intense symptoms of many kinds than men. Researchers have speculated that this may be due to differences in how women perceive the body, label their symptoms, describe their symptoms, or discuss them. Conventionally, women are more likely to acknol3ege and talk about physical discomfort.

Next Step: Getting the Brain Into Focus
Lawrence A. Bradley, PhD, has been working with images of blood flow in different regions of the brain as a sign of how actively these brain regions are working. Bradley says that people with fibromyalgia have differences in blood flow distribution in several brain areas involved in pain processing and pain modulation. He suspects that these differences may play a role in the abnormal pain sensitivity and other problems people with FM have. These studies also may reveal differences in brain function in women and men with FM. Bradley suggests that these neuro-imaging studies also may help researchers develop better ways of relieving fibromyalgia pain by providing a safe, accurate way to see if treatments are doing the right thing in the right part of the nervous system. 

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View other articles in vol. 10, no. 5 of FMOnline:
 
In the Spotlight
The Significance of Gender
 Are Men (With FM) Different From Women?

Men with FM
 
In the News
Gender and Drug Abuse
Menstrual Cycle Impacts FM Pain

Feeling Misunderstood?
Weighing in on Exercise

NFA News
A Look Back at Awareness Day

Make Fibromyalgia Visible

Artículos en Español
Hombres con FM