We aim to identify the gut microbiome composition in adults with CWP. We will collect the stool sample of 120 healthy individuals and 120 Chronic Widespread Pain patients. We hypothesize that the intestinal microbiota is altered in CWP compared to healthy subjects without CWP.

We aim to identify the variations in gut microbiota composition in Hong Kong adults with CWP. We hypothesize that the intestinal microbiota is altered in CWP compared to healthy control. The design of the study is a pilot case-control study with adults with CWP (n=120) and healthy adults without any chronic pain (n=120). Participants will be recruited in 8 general-outpatient clinics in the New Territories East region of Hong Kong.

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.

Participants will be recruited in 8 general-outpatient clinics in the New Territories East region of Hong Kong. Healthy participants with matching age and sex will be recruited from the general public.