Do women experience more pain than men?

Differences in anatomical, physiological, and hormonal features between men and women may help to explain why women are more sensitive to pain and experience more chronic orofacial pain, according to a clinical review in the Journal of the American Dental Association (July 2012, Vol. 143:7, pp. 764-765).

Understanding these differences "should help counteract prejudicial attitudes toward female patients, which can lead to inadequate care," wrote Thuan Dao, DMD, MSc, PhD, an associate professor at the University of Toronto Faculty of Dentistry.

Allegations that some pain experienced by female patients is psychosomatic could be because certain complaints of pain are difficult to substantiate quantitatively, Dr. Dao noted.

"Many recurrent pain disorders, especially those with a higher female prevalence, are of unknown origin, and sex-specific pains due to anatomical and hormonal differences ... more often are nonpathological in women," she wrote.

Several chronic pain conditions -- including temporomandibular disorders -- are more prevalent in women than in men, according to Dr. Dao. In addition, sex differences in orofacial pain emerge at puberty, peak during reproductive years, and decline at menopause, she added.

Growing body of evidence

Numerous epidemiologic and clinical studies have demonstrated that women are at higher risk for many clinical pain conditions, according to a 2009 literature review in the Journal of Pain (May 2009, Vol. 10:5, pp. 447-485).

"The growing body of evidence that has accumulated in the past 10 to 15 years continues to indicate substantial sex differences in clinical and experimental pain responses, and some evidence suggests that pain treatment responses may differ for women versus men," wrote the study authors, from the University of Florida College of Dentistry.

A related study published this year in the same journal analyzed data from the electronic medical records of 11,000 patients and found that, for several diagnoses, women's average pain score was at least one point higher than men's -- a clinically meaningful difference (March 2012, Vol. 13:3, pp. 228-234).

While there are few gender pain studies focused specifically on dental treatments, a study in the Journal of Contemporary Dental Practice involving 160 patients (89 men, 71 women) found that the level of pain felt by patients during endodontic treatment is "significantly correlated" with gender and pulp status, and that practitioners should be prepared to use supplemental local anesthesia in women (July 1, 2011, Vol. 12:4, pp. 301-304).

"The current study found a statistically significant association between gender and pain experienced during root canal treatment, with more women experiencing more pain," wrote the study authors, from the University of Nigeria College of Medicine.

Why?

While the evidence suggests that women and men do not experience pain in the same way or to the same degree, and that there is an overrepresentation of women with chronic orofacial pain, questions remain as to why, Dr. Dao noted.

A 2005 literature review in Gender Medicine noted that "although differences in pain sensitivity between women and men are partly attributable to social conditioning and to psychosocial factors, many laboratory studies of humans have described sex differences in sensitivity to noxious stimuli, suggesting that biological mechanisms underlie such differences" (September 2005, Vol. 2:3, pp. 137-145).

A number of other reasons also have been suggested, according to Dr. Dao:

• Women may seek treatment more readily than men when they have a physical problem.
• Men have been socialized to be more stoic, with some societies regarding pain endurance as a sign of virility.
• Differences in sex hormones, notably estrogen; "The structural and functional differences between male and female descending pain inhibitory systems, such as those responsible for opioid and nonopioid stress-induced analgesia, also appear to be influenced by sex hormones," Dr. Dao wrote.
• Differences in the structural organization and function of the nervous system.

In a 2000 literature review in the Journal of Orofacial Pain, Dr. Dao and her co-author examined whether the higher prevalence of chronic orofacial pain in women is a result of sex differences in generic pain mechanisms and "as-yet unidentified" factors unique to the craniofacial system (Summer 2000, Vol. 14:3, pp. 169-184).

"While evidence for sex differences in pain has not been established beyond doubt, distinct anatomic and hormonal features in women and men provide compelling clues that their pain might be modulated in a differential manner by a number of biologic factors," they wrote. "The cyclic fluctuations of various pain disorders across the menstrual cycle, along with gender differences in the composition of gonadal hormones, give rise to a number of hypotheses related to the actions of estrogen, progesterone, and testosterone."

Evaluation and treatment of pain patients should be performed on an individual basis, they recommended.

"In the treatment context, whether gender differences in pain exist is perhaps not the main issue; rather, our ultimate objective is to use all the available information about a patient, including his or her gender, in a judicious manner to improve treatment strategies and the quality of life of those who experience pain."