title: The epidemiology of chronic syndromes that are frequently unexplained: do they have common associated factors?
abstract: BACKGROUND
  Syndromes for which no physical or pathological changes can be found tend to be researched and managed in isolation although hypotheses suggest that they may be one entity. The objectives of our study were to investigate the co-occurrence, in the general population, of syndromes that are frequently unexplained and to evaluate whether they have common associated factors.
  
  
  METHODS
  We conducted a population-based cross-sectional survey that included 2,299 subjects who were registered with a General Medical Practice in North-west England and who completed full postal questionnaires (response rate 72%). The study investigated four chronic syndromes that are frequently unexplained: chronic widespread pain, chronic oro-facial pain, irritable bowel syndrome, and chronic fatigue. Validated instruments were used to measure the occurrence of syndromes and to collect information on a variety of associated factors: demographic (age, gender), psychosocial (anxiety, depression, illness behaviour), life stressors, and reporting of somatic symptoms.
  
  
  RESULTS
  We found that 587 subjects (27%) reported one or more syndromes: 404 (18%) reported one, 134 (6%) reported two, 34 (2%) reported three, and 15 (1%) reported all four syndromes. The occurrence of multiple syndromes was greater than would be expected by chance (P < 0.001). There were factors that were common across syndromes: female gender [odds ratio (OR) = 1.8; 95% confidence interval (95% CI) 1.5-2.2], high levels of aspects of health anxiety like health worry preoccupation (OR = 3.5; 95% CI 2.8-4.4) and reassurance seeking behaviour (OR = 1.4; 95% CI 1.1-1.7), reporting of other somatic symptoms (OR = 3.6; 95% CI 2.9-4.4), and reporting of recent adverse life events (OR = 2.3; 95% CI 1.9-2.8).
  
  
  CONCLUSIONS
  This study has shown that chronic syndromes that are frequently unexplained co-occur in the general population and share common associated factors. Primary care practitioners need to be aware of these characteristics so that management is appropriate at the outset.
authors.affiliation: Unit of Chronic Disease Epidemiology, School of Epidemiology and Health Sciences, The University of Manchester, Manchester, UK. vishal.r.aggarwal@manchester.ac.uk
authors.forename: Vishal R
authors.initials: VR
authors.lastname: Aggarwal
authors.forename: John
authors.initials: J
authors.lastname: McBeth
authors.forename: Joanna M
authors.initials: JM
authors.lastname: Zakrzewska
authors.forename: Mark
authors.initials: M
authors.lastname: Lunt
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Macfarlane
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000367:Age Factors; D000368:Aged; D001007:Anxiety / Q000150:complications; D001294:Attitude to Health; D015897:Comorbidity; D003430:Cross-Sectional Studies; D004739:England / Q000453:epidemiology; D005156:Facial Neuralgia / Q000453:epidemiology; D015673:Fatigue Syndrome, Chronic / Q000453:epidemiology; D005260:Female; D005356:Fibromyalgia / Q000453:epidemiology; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D011569:Psychiatric Status Rating Scales; D012307:Risk Factors; D012737:Sex Factors; D012803:Sick Role; D013001:Somatoform Disorders / Q000453:epidemiology* / Q000209:etiology / Q000523:psychology; D013315:Stress, Psychological / Q000150:complications; D013577:Syndrome