January 23rd, 2012
03:01 AM ET
The ache, the hurt, the burn, the stab. We use all kinds of words to describe pain, but the truth is that there’s no way to know if what you experience as pain differs from anyone else’s – it’s a matter of individual perception.
Scientists are honing in on a disparity between men and women that may exist in that perception. In the largest study of its kind, Stanford researchers analyzed electronic medical records for ratings of pain, and found that women tend to report greater amounts of pain in a variety of diagnoses. They report their results in Monday in the Journal of Pain.
The explanation could be that women are more vocal and forthcoming about the pain they experience, and that men are less so. But some pain doctors think the study reflects ongoing problems regarding the underdiagnosis and undertreatment of pain in women, and that there could even be biological underpinnings to this gap.
Researchers used electronic medical records from Stanford Hospital and Clinic for more than 72,000 patients. The records, when put together, contained more than 160,000 pain scores in more than 250 primary diagnoses. They narrowed this down to more than 11,000 patients with pain scores that had been recorded as part of their routine medical care.
They found the greatest differences in patients with musculoskeletal, circulatory, respiratory and digestive system disorders. There were also sex-specific differences in the intensiveness of pain in disorders of the cervical region and acute sinusitis. The findings make sense in the context of what experimental pain studies have found in the past.
On average, across many diseases, women reported experiencing pain one point higher than men on an 11-point scale. That may not seem like much, but a one-point difference can be used as an indication that a drug is working, said Dr. Atul Butte, senior author of the study and associate professor at Stanford University School of Medicine.
“We actually use these numbers. We use these as a kind of threshold – when do we start pain medicine? Are we treating someone with enough pain medicine?” he said. “We need to have that understanding that there is a sex difference here.”
In the data set, researchers used only the first pain score associated with a clinical visit. But there are certain caveats: Some patients may be represented in the sample multiple times. Researchers did not obtain information about patients’ use of over-the-counter drugs prior to their hospital visit, which could be a factor that influences pain reporting. Still, the large size of the data set means individual biases may be less of a factor than on smaller studies on pain.
Two pain scales were used: verbal and non-verbal (based on an external observer). Adult patients were asked to rate their pain from 0, meaning “no pain” to 11, meaning “worst pain imaginable.” For patients unable to communicate, trained personnel assessed them on an 11-point scale. However, another problem with the study is that most records didn’t identify whether it was the patient or observer who rated the pain.
There are a variety of possible explanations for these findings, including hormones, genetics or psychological factors. The stage of the menstrual cycle may affect women’s reporting of their pain, for example.
Study authors also note that women are more likely to seek medical care than men, and that the gender of the evaluating physician may affect how patients report their pain.
But even if more women go to the doctor, that doesn’t mean they are getting the treatment they need, said Dr. Gaurav Trehan, director of interventional pain medicine at Temple University Hospital in Philadelphia, who did not contribute to this study.
Other research has suggested that women have more severe, frequent and longer-lasting pain than men generally. Laboratory studies of pain inflicted on participants have also found that women generally have a lower pain threshold than men.
“A lot of times cognitive, emotional and behavioral factors really influence the level and someone’s experience with pain,” said Dr. Irene Wu, assistant clinical professor of anesthesiology at UCLA Medical Center, who was not involved with the study. She said women's stress may also make pain seem worse.
From Wu’s experience, women tend to point to multiple areas of their body that give them pain, whereas men are more concise and complain of pain in one part specifically. She notes that chronic pain conditions that are more common in women, such as fibromyalgia, can compound women’s pain experience in general.
Similarly, women also tend to let their pain build up in various areas, so that by the time they get to a doctor there are a lot of spots that need to be addressed, she said.
“They take it in a lot more and for longer periods of time, so when it does accumulate, it may seem like at the doctor’s office their pain is so much more severe than men’s pain is,” she said.
And it may be that because of the popular notion that women can tolerate more pain than men – they often go through childbirth and decades of menstrual cramps, for instance – women do not receive adequate pain medications, Trehan said.
Other groups of scientists are looking at what happens in the brain when men and women experience pain, to see if there is a biological basis for their differing perceptions. Preliminary studies have found that there may be parts of the brain more active in men than in women when pain is induced, Trehan said.
Further research is needed to better understand what underlies this apparent sex difference in the experience of pain.
"We need to look beyond the pain," Wu said. "We need to treat the pain from a medical perspective, but I think we also need to make sure, and adequately assess, how well the patient is dealing with the pain."
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