In contrast, no other significant sex differences were found in terms of fibromyalgia symptom severity.
The study, “Sex-Related Differences in Symptoms and Psychosocial Outcomes in Patients With Fibromyalgia: A Prospective Questionnaire Study,” was conducted by a team from the Mayo Clinic. It was published in the journal Mayo Clinic Proceedings: Innovations, Quality & Outcomes.
Fibromyalgia is more common in women than in men; more than four out of every five people with the pain disorder are female. However, whether there are sex-based differences regarding symptoms and clinical outcomes among fibromyalgia patients is still unclear. Notably, prior studies have reported contradictory results.
“Given the degree of variability in previous study findings, the objective of our prospective questionnaire study was to explore the association between sex and various clinical symptoms and psychosocial outcomes in the FM [fibromyalgia] patient population,” the researchers wrote.
Responses were collected from 668 patients who were referred to the Fibromyalgia and Chronic Fatigue Clinic at Mayo. Nearly 91% of the patients were women (606), and the mean age was 47.2 years.
The participants completed a variety of questionnaires related to fibromyalgia and its symptoms, to include the Revised Fibromyalgia Impact Questionnaire (FIQ-R), the Multidimensional Fatigue Inventory, and the Medical Outcomes Study Sleep Scale. Demographic and clinical data, obtained from electronic health records, also were assessed.
The results showed no significant sex-based differences in terms of demographic factors; in the overall group, about 90% of the patients were white, about three-quarters were married, and nearly three-quarters had completed more than 12 years of formal education.
Initial analyses indicated a significant association between female sex and higher tender point count, lower FIQ-R score (indicating less severe symptoms), and vitality — measured on a subscale of the 36-Item Short Form Health Survey. After doing additional statistical adjustments, only the association with tender point count remained statistically significant.
“Our study demonstrated that female sex may be a risk factor for greater TPC [tender point count] than male sex,” the researchers wrote.
Among potential explanations for this difference, the team included prior evidence of a lower pain threshold in women, possible influences from hormones, and other factors such as different expectations.
The scientists also said that old diagnostic criteria for fibromyalgia emphasized tender point count, whereas more recent criteria, revised in 2010, do not. As such, it is possible that the difference in diagnostic criteria would lead to sex-based differences in diagnosis.
“Future studies should investigate whether the association of female sex and greater TPC remains significant if using solely the 2010 American College of Rheumatology Fibromyalgia Diagnostic Criteria for FM diagnosis,” the researchers wrote.
They added that research with larger sample sizes, particularly larger numbers of males, is needed.
“Furthermore, studies should investigate whether sex-related differences persist longitudinally over time and how individualized therapy and management can be implemented based on sex-related differences,” the researchers concluded.