Exploring gender differences, medical history, and treatments used in patients with fibromyalgia in the UK using primary-care data: a retrospective, population-based, cohort study

Background Fibromyalgia mainly affects women (80–90% of cases), but some contradictory studies have shown lower estimates (59% of cases affecting women). Psychosocial impacts of fibromyalgia are similar in men and women, but men delay seeking medical help. Subsequent revisions of the 1990 American College of Rheumatology fibromyalgia classification criteria removed the requirement for at least 11 of 18 tender point sites, which led to various prevalence estimates and women to men ratios in the general population. We aimed to measure new cases of fibromyalgia to determine whether the sex ratio has changed after criteria revisions and to explore the symptoms and treatment. Methods This retrospective, population-based, cohort study was done in the UK (Wales) using primary-care electronic health data from the Secure Anonymised Information Linkage. Individuals aged 18 years or older with a first mention of fibromyalgia using READ codes (N239 and N248) were included and stratified by gender, which was coded as men or women. Cases of fibromyalgia were calculated at three 5-year periods (period 1 defined as 2004–08, period 2 defined as 2009–13, and period 3 defined as 2014–18). Descriptive analyses were performed on variables according to gender. Findings Between Jan 1, 2004, and Dec 31, 2018, data on 22 568 individuals with fibromyalgia were extracted. The mean age of participants was 48 years (SD 13) and 20 040 (88·8%) were women. In period 1, among 5296 new cases of fibromyalgia, 784 (14·8%) were men and 4512 (85·2%) were women. In period 2, 642 (10·8%) of 5958 new cases were men and 5316 (89·2%) were women, and in period 3, 1102 (9·7%) of 11 314 new cases were men and 10 212 (90·3%) were women. Women had a significantly higher BMI than men (difference 1·6%, 95% CI 1·5–1·7; p<0·01) and more widespread pain based on READ code (2·9%, 95% CI 1·8–4·0; p<0·05). Men had significantly more comorbidities; however, women had more gastrointestinal disorders (difference of 10·0%, 95% CI 8·4–11·4; p<0·01). A significantly higher number of women received steroids (difference of 8·3%, 6·3–10·3; p<0·01), antidepressants (5·4%, 4·2–6·6; p<0·01), and anxiolytics and barbiturates (7·2%, 5·2–9·2; p<0·01), whereas more men received gabapentin (9%, 7·0–11·0; p<0·01). Interpretation Routine health data does not show an increase of fibromyalgia in men compared with women, despite revisions to classification criteria. Men had significantly more comorbidities, except for gastrointestinal disorders. The sex differences in fibromyalgia treatment might represent clinician or patient choice and are worth exploring in future studies. Funding None