Fecal Microbiome in Women With Fibromyalgia: Functional Composition and Symptom Correlations.

Objective: To describe the composition of the gut microbiota of women living with fibromyalgia, compared with controls, and examine the relationship between fecal microbiota and clinical features of fibromyalgia.

Methods: New Zealand women meeting American College of Rheumatology fibromyalgia criteria and age-matched controls provided fecal samples and completed validated surveys assessing pain, disorders of gut-brain interaction (DGBI), headaches, sleep quality, oral health, cognition, anxiety, depression, diet, and quality of life. Metatranscriptomic analysis identified phyla, genera, and species in fecal samples. Correlation coefficients were calculated for each α-diversity metric against clinical variables. Welch's t-test or Wilcoxon rank test was applied for binary clinical variables. Generalized linear models analyzed associations in the fibromyalgia group, adjusting for age, body mass index, and diet. Data processing and analysis used R version 4.2.1, with the Benjamini-Hochberg formula controlling for false discovery rate at ≤0.10 to minimize type 1 error risk.

Results: No statistically significant differences were seen in the microbial expression in fecal samples of women with fibromyalgia (n = 104) compared with controls (n = 52). Significant associations among three species from the Bacteroidetes phylum and cognitive impairment were observed. Fusobacteriota was significantly associated with Rome IV(B) DGBI, specifically epigastric pain syndrome. A strong association was observed between oral microbiota in feces and upper gastrointestinal DGBI, indicating both negative and positive correlations in this population.

Conclusion: No overall differences in fecal microbial expression were found in women with fibromyalgia. However, Bacteroidetes and Fusobacteriota phyla were significantly associated with cognitive impairment and epigastric pain syndrome, respectively.