Circulating leptin levels in patients with myalgic encephalomyelitis, chronic fatigue syndrome or fibromyalgia: a systematic review protocol

Objective: The objective of the review is to evaluate circulating levels of leptin in people diagnosed with myalgic encephalomyelitis chronic fatigue syndrome or fibromyalgia syndrome and to investigate the differences compared with healthy controls. Introduction: Myalgic encephalomyelitis chronic fatigue syndrome is a condition that has major symptoms, including self-reported fatigue, post-exertional malaise, and unexplained pain across the body. The widespread pain is measured in a systematic way and is often referred to as fibromyalgia. The two disorders have many similarities, but their association with leptin has indicated that leptin may affect the role of pro-inflammatory cytokines and symptom severity. Inclusion criteria: This review will consider observational studies of varying study designs including prospective and retrospective cohort studies, case-control studies, time-series, and analytical cross-sectional studies that include both cases and healthy comparators. Cases will include a diagnosis of myalgic encephalomyelitis, chronic fatigue syndrome, and/or fibromyalgia. Controls are people without this diagnosis, usually healthy participants. Only studies published in English will be included due to limited resources for translation. Methods: This protocol will be reported based on the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) checklist and will follow the JBI methodology for systematic reviews of etiology and risk. A comprehensive search strategy will include PubMed, Embase, Scopus, Science Direct, and PsycINFO. Two reviewers will screen, critically appraise eligible articles, and extract data using a standardized data extraction tool informed by JBI SUMARI. The authors will complete a quantitative analysis that synthesizes findings across studies using pooled effect sizes and confidence intervals of the measures provided. Systematic review registration number: PROSPERO CRD42020169903

Automated summary

The study aims to evaluate circulating levels of leptin in individuals diagnosed with myalgic encephalomyelitis chronic fatigue syndrome or fibromyalgia syndrome compared to healthy controls. The conditions are characterized by symptoms such as fatigue, post-exertional malaise, and widespread unexplained pain, with the association with leptin suggesting a potential impact on pro-inflammatory cytokines and symptom severity.