Do women feel more pain than men?
It has long been known that certain pain-related conditions, like fibromyalgia, migraine and irritable bowel syndrome, are more common in women than in men. And chronic pain after childbirth is surprisingly common; the Institute of Medicine recently found that 18 per cent of women who have cesarean deliveries and 10 per cent who have vaginal deliveries report still being in pain a year later.
But new research from Stanford University suggests that even when men and women have the same condition — whether it’s a back problem, arthritis or a sinus infection — women appear to suffer more from the pain.
Last year, the Institute of Medicine estimated that chronic pain afflicts 116 million Americans, far more than believed. But these latest findings, believed to be the largest study ever to compare pain levels in men and women, raise new questions about whether women are shouldering a disproportionate burden of chronic pain and suggest a need for more gender-specific pain research.
The study, published Monday in The Journal of Pain, analyzes data from the electronic medical records of 11,000 patients whose pain scores were recorded as a routine part of their care. (To obtain pain scores, doctors ask patients to describe their pain on a scale from 0, for no pain, to 10, "worst pain imaginable.")
For 21 of 22 ailments with sample sizes large enough to make a meaningful comparison, the researchers found that women reported higher levels of pain than men. For back pain, women reported a score of 6.03, men 5.53. For joint and inflammatory pain, it was women 6.00, men 4.93. Women reported much higher pain levels with diabetes, hypertension, ankle injuries and even sinus infections.
For several diagnoses, women’s average pain score was at least one point higher than men’s, considered a clinically meaningful difference. Overall, their pain levels were about 20 per cent higher than men’s.
Unfortunately, the data don’t offer any clues as to why women report higher pain levels. One possibility is that men have been socialized to be more stoic, so they underreport pain. But the study’s senior author, Dr. Atul Butte, an associate professor at Stanford’s medical school, said that explanation probably did not account for the gender gap.
"While you can imagine such a bias," he said, "across studies, across thousands of patients, it’s hard to believe men are like this. You have to think about biological causes for the difference."
An extensive 2007 report by the International Association for the Study of Pain cited studies showing that sex hormones may play a role in pain response. In fact, some of the gender differences, particularly regarding headache and abdominal pain, begin to diminish after women reach menopause.
Research also suggests that men and women have different responses to anesthesia and pain drugs, reporting different levels of efficacy and side effects.
One reason for the lack of information about sex differences is that many pain studies, in both animals and humans, are done only in males. One analysis found that 79 per cent of the animal studies published in a pain journal over a decade included only male subjects, compared with eight per cent that used only female animals.
