Scientists investigating gender differences in pain have found that not only do women report more pain throughout the course of their lifetime, they also experience it in more bodily areas, more often and for longer duration when compared to men.
There also seem to be differences in how men and women think and feel about their pain. For example, anxiety may affect men and women in different ways, and the strategies used to cope with pain may actually make their experience worse.
These conclusions are based on several studies into the pain response of volunteers exposed to a pain stimulus, such as a cold water bath, as well as field studies in clinics and hospitals.
"Until fairly recently it was controversial to suggest that there were any differences between males and females in the perception and experience of pain, but that is no longer the case," said Dr Ed Keogh a psychologist from the Pain Management Unit at the University of Bath*.
"Research is telling us that women experience a greater number of pain episodes across their lifespan than men, in more bodily areas and with greater frequency.
"Unfortunately all too often the differences between males and females are not considered in pain research or practice, and instead are either ignored or statistically averaged."
There remains much discussion in the scientific community about why these gender differences in pain exist.
"While most explanations concentrate on biological mechanisms, such as genetic and hormonal differences, it is becoming increasingly clear that social and psychological factors are also important," said Dr Keogh.
One example of this is the different strategies men and women use to cope with pain. Whilst women tend to focus on the emotional aspects of pain they experience, men tend to focus on the sensory aspects, for example concentrating on the physical sensations they experience.
"Our research has shown that whilst the sensory-focused strategies used by men helped increase their pain threshold and tolerance of pain, it was unlikely to have any benefit for women," said Dr Keogh.
"Women who concentrate on the emotional aspects of their pain may actually experience more pain as a result, possibly because the emotions associated with pain are negative."
To carry out this research, scientists asked volunteers to place their non-dominant arm in a warm water bath (37 degrees centigrade) for two minutes before transferring the hand into an ice water bath maintained at a temperature of 1 - 2 degrees centigrade.
The cold pressor tank allows researchers to monitor the pain threshold (the point at which volunteers first notice the pain) and pain tolerance (the point at which volunteers can no longer stand the pain). An upper time limit of two minutes is used in these kinds of studies.
Other research by the Pain Management Unit has looked at the relationship between gender differences in anxiety sensitivity and pain. Anxiety sensitivity is the tendency to be fearful of anxiety-related sensations (e.g., rapidly beating heat), and seems to be important in the experience of pain sensations. In a study of 150 patients referred to a hospital clinic with chest pain, researchers discovered that the factors that predicted pain in men and women were different.
Researchers believe that it is the fear of anxiety-related sensations and an increased tendency to negatively interpret such sensations, both of which are more predominant in women than men that influences women's experiences of pain.
"Chest pain is associated with coronary heart disease, angina and heart attacks, so it is understandable that chest pain is a cause of great anxiety for patients and that anxiety has an important role in the experience of chest pain," said Dr Keogh.
"This research is also consistent with studies that suggest that men and women experience chest pain in different ways and that, compared to men, women can sometimes report more intensive pain and nausea."
Another study has shown that interdisciplinary approaches to pain management may have different effects on women than men.
Working with the Royal National Hospital for Rheumatic Diseases in Bath, researchers from the Pain Management Unit carried out assessments on 98 patients in chronic pain as they went through a pain management programme involving physiotherapy, psychological treatments and occupational therapy.
Whilst both men and women exhibited a significant reduction in pain intensity both during and immediately after the programme, three months later women reported the same levels of pain as pre-treatment, whereas men's remained the same as immediately post-treatment. Interestingly, there were improvements in disability, in both sexes, which were maintained at follow-up. This suggested that there may also be important differences in pain experiences and improvements in disability.
"Gender can be profitably examined as a potential predictor of pain experience, and in particular, pain following treatment, but it is too early to say exactly how gender-specific interventions can be tailored to address these potentially important differences," said Dr Keogh.
"However, evidence is certainly converging to suggest that accounting for greater differences may increase the overall effectiveness of treatments."