Sunday, February 20, 2011

Gender Myths Can Be a Real Pain Sometimes

There’s an old joke that goes something like this. A man is in the delivery room watching his wife give birth in excruciating pain. In distress, he asks the obstetrician, “Doc, isn’t there anything you can do to alleviate my wife’s pain?” “There sure is” the doctor replies. “We’ve got a device that automatically transfers the mother’s pain to the father. Would you like to give it a go?” The husband nods his head, and the doctor says “we’ll start by transferring 25% of your wife’s pain.” He turns the knob and flicks the switch and the wife immediately stops crying out in pain. The husband hardly feels a thing. “That’s surprising” the doctor says. “Let’s try transferring 50% of the pain.” Once again, the wife immediately feels better, and actually begins to relax. The husband says “This isn’t bad at all, Doc, give me all of my wife’s pain.” The doctor, in almost complete disbelief, turns the knob all the way to 100% and flicks the switch. The husband doesn’t even flinch. “That’s amazing!” the doctor exclaims. “Most men can’t get beyond 50%.” The next day the husband and wife return home with their new baby only to find the milkman dead on their doorstep.

Just how pervasive is the belief that women have a higher tolerance for pain than men? In the popular Discovery Channel program Myth Busters (, hosts Jamie Hyneman and Adam Savage attempt to scientifically test various myths and truisms found in popular culture. It’s a good show. I have my kids watch it with me and generally we learn something about science. In short, if your kids have to watch TV, Myth Busters is a pretty good program for them to watch.

In one episode, Adam and Jamie tested whether women have higher pain thresholds and tolerance levels than men. The methodology was simple, and in many ways comparable to laboratory studies published in medical journals. The participant submerges their right hand into freezing water to just below the elbow. First, they indicate when it becomes painful, which is timed (i.e. the pain threshold); then they tolerate the pain for as long as possible up to a limit of 3 minutes. The submersion of the forearm in freezing water is known as the cold pressor test in the medical literature.

The results indicated that women lasted 16.1 seconds longer (100.4 to 84.3), on average than men, leading Adam to enthusiastically conclude the myth has been “confirmed”, to use the familiar parlance of the Myth Busters host. In other words, it’s true – women do have higher pain thresholds and higher tolerance levels than men. Of course, Adam’s enthusiasm fades quickly as he feigns a sudden recognition that, as a man, he is therefore a member of the weaker sex, at least in this context.

There was no test for the statistical reliability of the results, but even if we assumed that this difference is statistically significant, there are some fairly obvious reasons why this result might differ from the plethora of published research showing that men have higher pain thresholds and higher levels of pain tolerance, even studies specifically examining submersion of the hand in freezing water.

First, limiting participants to 3 minutes is a problem. We tend to think in terms of averages. It is relatively easy to comprehend that men are, on average, better or worse at something than are women. But to understand the whole story, we need to look at the entire distribution of results, or in this case the entire range of possible submersion times. If there are more men than women at the extreme end of the distribution who could have withstood the pain for far more than 3 minutes, than arbitrarily limiting the maximum duration skews the results.

The more obvious problem with the method is, of course, the presence of the television camera. Participants knew they were going to be on a TV program, and perhaps even that the myth being tested was whether or not women withstand pain better than men do. Conforming to perceived interests of the hosts seems a distinct possibility. So this result is questionable on scientific grounds, even though it makes for good television.

It turns out that medical research simply does not support the notion that women can handle pain better than men. Whether it examines pain thresholds, pain tolerance levels, or subjective ratings of painfulness, men seem to handle pain better than women. In fact, this finding is so well established in the literature, that most articles simply assert this as a fact and then report on mediating variables (i.e., the processes which allow men to endure more pain), or moderating variables (i.e., the conditions under which men can endure more pain).

In contrast to the “confirmed” conclusion on Myth Busters, more reliable research published in top medical journals indicates that men can tolerate submerging various body parts in freezing water longer than women; and it turns out that submersion in freezing water is not the only type of pain that men seem to endure better than women. Other cold stimuli produce similar results. For example, attaching an extremely cold “thermode” to various parts of the body yields the same conclusion – men can tolerate colder temperatures than women.

What about when temperatures move to the other extreme? Same result. Women are more sensitive to heat pain on their skin. Research involving electrical shocks to the fingers and other regions of the body also shows that men have a higher level of pain tolerance. Indeed, women seem to have more sensitive fingers than men in general. In another study, pricks to the tips of fingers with pin-like objects produced higher ratings of pain in women compared to men. And finally, men can tolerate greater amounts of pressure applied to their fingers and toes.

Studies also show that women report more post-operative dental pain than men, and choose stronger pain relievers. Women rate cholecystectomies, a procedure for removing cysts from the gall bladder, as more painful, and they require greater doses of pain killers compared to men. One week after cardiac surgery female patients report pain in more regions of their bodies than do male patients. Even the act of administering anaesthesia prior to surgery is more painful for women.

Women seem to get headaches a lot, especially when their male partners want to have sex (another unfortunate gender myth I'm afraid). Well, research indicates that women do get headaches more often than men – twice as often in one study. They also report higher levels of pain while experiencing headaches. The pressure pain threshold is higher for men at virtually any point on the body, with one exception, their arses. When it comes to the old gluteus, there’s no difference between the sexes. Women report being tired and stressed out more often than men. Pre-pubescent, grade school girls report abdominal pain more frequently than boys of the same age.

Some researchers have suggested that one key moderating variable is whether the painful stimulus is short-lived or must be endured over time. The reasoning is that women may have higher levels of endurance because that corresponds more with giving birth, a process that takes hours, even days. However, research doesn’t support such a contention. In one study, a blood pressure device (called a “sphygmomanometer” believe it or not), was used to create pressure around the forearm, then participants were asked to squeeze a grip strength device (called a “dynamometer”) for up to 20 minutes. The use of forearm muscles combined with the pressure around them becomes painful fairly quickly, yet men held out longer than women. Mind you, we’re talking about 20 minutes here. It’s not clear that men would hold out longer when the maximum duration was 20 hours, and many, many women endure deliveries exceeding 20 hours.

Perhaps my favourite study is one that focused an argon laser on the hands of men and women. How, exactly, does one get approval from a university ethics committee to shoot participants with laser beams? Cool! Today I get to go to work and shoot people with lasers! My 10-year old son would be impressed. Anyway, the results were not surprising. Women reported pain at lower levels of laser intensity, and their maximum tolerance levels were also lower than the corresponding levels for men.

Men are also almost twice as likely to return to playing a sport after joint replacement surgery. Given that pain is the number one reason given for not returning to a sport after this kind of surgery, this result implies that men have a higher tolerance for this kind of pain as well. Women also report higher levels of pain experienced during a variety of illnesses, and for various forms of chronic pain. For a given illness, medical records indicate that women are more likely to report being ill, visit a doctor, visit a hospital, and stay longer in hospital than men, again suggesting less tolerance for pain and discomfort.

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