Women experience more severe pain, more often and for longer than men but are less likely to get the right treatment, researchers have discovered.
Different hormones, body composition and central nervous systems means women are more susceptible to a range of painful conditions, according to the International Association for the Study of Pain.
Better understanding among health professionals of sex differences in pain could save lives, prevent thousands of sick days, and would save the country millions of pounds, an international pain conference in Glasgow was told last week.
The majority of doctors are ignorant about research revealing genetic, biological and hormonal differences in the way pain affects women. Many are unaware that common treatments such as paracetamol are less effective for women and that they are more likely to suffer side effects.
Long-term conditions such as migraines, irritable bowel syndrome, arthritis and fibromylagia are much more widespread in women.
Despite this, many women are still not believed by doctors and given a psychiatric diagnosis instead. Depression often accompanies pain but it is rarely the cause.
Dr Beverly Collett, consultant at Leicester's pain management service and chair of the Chronic Pain Policy Coalition, said: "It is only in the past 10 years we have started to understand these differences, and it remains an under-researched area. But even the knowledge we have has not filtered down and the average GP has no idea that drugs such as paracetamol and morphine work differently in women."
An extensive Swedish study last year confirmed that women having heart attacks are more likely to feel generalised pain in their shoulders and back rather than shooting pain in the chest and left arm. Most doctors and nurses are unaware of these differences, which has life-threatening consequences for women, said Dr Collett.
Until recently, most pain studies were carried out on male rodents, and the majority of drug trials on men. Researchers started to investigate sex differences less than 10 years ago.
Work by brain imaging experts at Oxford University has found women with untreated painful periods are more likely to react to other painful stimuli because of changes in the brain. These findings suggest that untreated persistent pain makes women more susceptible to a lifetime of painful conditions.
Professor Irene Tracey, director of the Oxford Centre for Functional Magnetic Resonance Imaging of the Brain, said: "Our preliminary data suggests there are long-term health consequences of not taking monthly period pain seriously. The images show increased activity in different brain regions which suggests untreated pain permanently changes the brain and central nervous system. This could explain why multiple painful conditions are much more common in women."
She added: "The next stage for us it to find out whether these changes are permanent, or if this is recoverable when the pain is treated properly."
One in eight people in the UK suffers from migraine. The attacks are three times more common in women, and tend to last for longer than in men. Pioneering research by Dr Ann McGregor at the City of London Migraine Clinic has found a strong link between migraines and low oestrogen levels, common during menstruation and after the menopause.
England has no NHS strategy for tackling pain, while Scotland does. Nearly eight million Britons suffer with chronic pain. Lord Darzi, the junior health minister, did not mention it in his recent wholesale review of the health service.
Experts believe pain should be recognised as a disease in its own right. Dr Collett said: "Better access to multidisciplinary pain services is essential for these women. The economic and social benefits for society are clear."
Car accident has led to a life of agony
Rosanna Notaro, 36, from north London, has been in pain ever since a serious car crash in 2003. Her initial injury was to her neck, but she now suffers from severe backache, migraines and stomach problems which have left her anxious and unable to work. Her pain is worse during her period, but she doesn't understand why. Her first GP didn't believe her, and she was forced to spend thousands of pounds on private doctors and therapists. Her new GP finally referred her two years ago to an NHS pain clinic, where she hopes to see a specialist doctor and psychologist. She is still on the waiting list.
Ms Notaro said: "At first, I presumed the pain would eventually go away and I would get better. I didn't expect to develop chronic pain, or that it would stop me working and lead me to consider suicide. My problems have arisen from a combination of an initial misdiagnosis and inappropriate treatments. I'm taking 20 tablets every day, but still some days I can't get up. I just want my life back."
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