October 14, 2010
Women suffer more chronic pain than men but there has been little effort to find out why, writes Judy Foreman.
It’s one of the more puzzling observations in medicine: the vast majority of chronic pain patients are women. Women suffer disproportionately from irritable bowel syndrome, fibromyalgia, headaches (especially migraines), pain caused by damage to the nervous system, osteoarthritis, jaw problems such as temporomandibular joint disorder (TMD) and much more. Women also report more acute pain than men after the same common surgeries.
In the lab, when researchers ask male and female volunteers to subject themselves to experimental pain – increasingly hot stimulation on the inner arm, immersion of the hand in very cold water, electrical jolts to the skin – women show lower pain thresholds (that is, they report pain at lower levels of stimulus intensity) and lower tolerance (they can’t bear intense pain as long).
Women are also better able to detect small gradations in pain stimuli and respond differently to certain opioid – painkilling – drugs. (It’s not clear if men and women differ in sensitivity to cancer pain.)
But it’s only recently that researchers have begun to study the exact genetic, physiological, hormonal and psycho-social factors that may underlie these sex differences. In part, that’s because pain researchers have been hampered by one rather shocking fact: most basic pain research is still done in male mice and rats.
”This has been a catastrophe,” McGill University pain geneticist Jeffrey Mogil says. He says the old rationale that menstrual cycles make females too difficult to study is bogus. Men and women, in fact, can be so different in the way their nervous systems process pain that one day there may be ”pink pills for women and blue pills for men,” he says. The lopsided research exists solely because of ”inertia”, he adds.