Probiotics for fibromyalgia: study design for a pilot double-blind, randomized controlled trial

Background: Fibromyalgia syndrome (FMS) is a chronic, generalized and diffuse pain disorder accompanied by other symptoms such as emotional and cognitive deficits. The FMS patients show a high prevalence of gastrointestinal symptoms. Recently it has been found that microbes in the gut may regulate brain processes through the gut-microbiota-brain axis, modulating thus affection, motivation and higher cognitive functions. Therefore, the use of probiotics might be a new treatment that could improve the physical, psychological and cognitive state in FMS; however, no evidence about this issue is available. Methods: This paper describes the design and protocol of a double-blind, placebo-controlled and randomized pilot study. We use validated questionnaires, cognitive task through E-Prime and biological measures like urine cortisol and stool fecal samples. The trial aim is to explore the effects of eight weeks of probiotics therapy in physical (pain, impact of the FMS and quality of life), emotional (depression, and anxiety) and cognitive symptoms (attention, memory, and impulsivity) in FMS patients as compared to placebo. Conclusion: This pilot study is the first, to our knowledge, to evaluate the effects of probiotics in FMS. The primary hypothesis was that FMS patients will show a better performance on cognitive tasks, and an improvement in emotional and physical symptoms. These results will contribute to a better understanding in the gut-brain axis. Here we present the design and protocol of the study.