Gut Microbiota in Adults With Chronic Widespread Pain

Inclusion Criteria: 1. Participants with Chronic Widespread pain Participants will be asked, "In the past 3 months, have you had pain in your muscles, bones and joints lasting at least 1 week?", as a screening question for CWP. To meet the criteria for CWP, subjects have to report musculoskeletal pain in at least 4 of 5 body regions and in at least 3 or more body quadrants (as defined by upper-lower/left-right side of the body) and axial skeleton (neck, back, chest, and abdomen), with pain duration of more than 3 months. A Widespread Pain Index (WPI) will be generated based on the number of pain sites. Subgroup of patients with fibromyalgia will be identified according to The American College of Rheumatology 2016 when subjects WPI of ≥ 7 and a symptom severity scale (SSS) score of ≥ 5 or a WPI between 4 and 6 and an SSS score of ≥ 9. 2. Healthy Participants Healthy participants will be those without chronic pain and depression. A screening question 'In the past 3 months, have you had pain in your muscles, bones and joints lasting at least 1 week?' will be asked to determine whether participant has chronic pain. Depression status will be determined by the questionnaire "Patient Health Questionnaire-9" Exclusion Criteria: * Participants with major chronic illnesses, such as malignancy, active inflammatory diseases, autoimmune diseases and metabolic diseases such as diabetes mellitus and thyroid diseases etc.; use of antibiotics, probiotics or prebiotics in the preceding 2 months, any acute illness in the preceding month, change in regularly taken medication in the preceding month, and substantial dietary alterations in the preceding month.