title: The classification of patients with chronic pain: age and sex differences.
abstract: OBJECTIVE
  To further develop an empirically based classification system for chronic pain patients through the examination of age and sex differences, and incorporation of pain duration in the grouping algorithm.
  
  
  METHODS
  Three hundred seventy-four chronic pain patients (300 aged 13 to 59 years; 74 aged 60 to 89 years) assessed at an outpatient, multidisciplinary pain management centre.
  
  
  METHODS
  Patients completed measures of demographic and descriptive information, pain intensity (box rating scale), perceived disability (modified Pain Disability Index) and affective distress (Symptom Checklist-90 Revised) before multidisciplinary treatment. Standardized scores from the assessment measures were entered into a series of hierarchical, multivariate cluster analyses to identify underlying patient subgroups.
  
  
  RESULTS
  Age-based patient groupings from prior research were partially replicated. Significant differences in clinical presentations were observed across age and sex groups. Pain duration was found to make an important contribution to the patient groupings. 'Good control' (low pain, disability, distress) and variants of 'chronic pain syndrome' (elevated pain, disability, distress) groupings were identified across all analyses. Two variants of a 'stoic' profile were identified among older patients, with low levels of distress relative to pain and perceived disability. One of these profiles was associated with long pain duration and was found only among males. Several unique clinical profiles were identified for female patients.
  
  
  CONCLUSIONS
  There are important age and sex differences in the clinical presentations of chronic pain patients. Some older patients present with unique clinical profiles that may reflect cohort differences, and/or physiological or psychological adjustment processes. There appears to be a greater number of distinct chronic pain presentations among females. Research on the classification of chronic pain patients within homogeneous diagnostic subgroups is needed.
authors.affiliation: Department of Anesthesiology, Division of Pain Management, University of Virginia Health System, Charlottesville, Virginia 22908, USA. ajcook@virginia.edu
authors.forename: A J
authors.initials: AJ
authors.lastname: Cook
authors.forename: D C
authors.initials: DC
authors.lastname: Chastain
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D016009:Chi-Square Distribution; D002908:Chronic Disease; D016000:Cluster Analysis; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010146:Pain / Q000145:classification* / Q000453:epidemiology / Q000503:physiopathology* / Q000523:psychology; D010361:Patients / Q000145:classification* / Q000523:psychology / Q000706:statistics & numerical data; D012727:Sex Characteristics