text: Sociodemographic and health-related information 
  Participants completed a standard intake questionnaire 
  form previously used in our clinical studies that assessed 
  age, sex, race, and insurance provider type. This ques- 
  tionnaire also assessed health-related variables included 
  anatomical region of primary pain complaint (low back, 
  neck, shoulder, or knee) and whether the patient had 
  undergone surgery for their primary pain complaints 
  (yes or no). Due to small cell sizes for certain categories, 
  race was dichotomized as white or non-white. For insur- 
  ance type, participants were asked to choose one of the 
  following options: private, public (Medicare and/or Me- 
  dicaid), uninsured/self-pay, worker’s compensation, and 
  other/commercial insurance. Among the study sample, 
  we observed few with no insurance (n = 7) or worker’s 
  compensation (n = 14). The study also included relatively 
  few with ‘other/commercial insurance’ (n = 45). Within 
  this group, informal assessment of these various plans 
  suggested high heterogeneity of plan characteristics and 
  coverage. Due to the small number of subjects in these 
  individual insurance strata and to improve interpretabil- 
  ity of results, we collapsed those reporting no insurance, 
  worker’s compensation and other/commercial insurance 
  into a single category (i.e., ‘Other’). Therefore, insurance 
  type was categorized as private, public, or other (no in- 
  surance, worker’s compensation, or other/commercial 
  insurance) for purposes of analysis. 