title: Modeling the indirect economic implications of musculoskeletal disorders and treatment.
abstract: BACKGROUND
  Musculoskeletal disorders impose a substantial economic burden on American society, but few studies have examined the economic benefits associated with treating such disorders. The purpose of this research is to estimate the indirect economic implications of activity limitations associated with musculoskeletal disorders and to quantifying the potential economic gains from elective surgery to treat arthritis of the knee and hip.
  
  
  METHODS
  Using regression analysis with the National Health Interview Survey (2004-2010 data, n=185,829 adults) we quantify the relationship between severity of activity limitations (walking, sitting, standing, etc.) and employment, household income, missed work days, and receipt of supplemental security income for disability. Activity limitations are combined to create an index similar to the Functional Ability Index from the Short Form 36 Health Questionnaire (SF-36) often used in clinical trials to measure patient functional mobility. This index is included in the regression analyses. We use data from published, prospective clinical trials to establish the improvement in patient functional ability following surgery to treat arthritis of the knee and hip.
  
  
  RESULTS
  Improved physical function is associated with higher likelihood of employment, higher household income and fewer missed work days for those who are employed, and reduced likelihood of receiving supplemental security income for disability. The magnitude of the impact and statistical significance vary by activity limitation and severity. Each percentage point increase in the index value is associated with a 2-percentage-point increase in the odds of being employed, a 3-percentage-point-day decline in work days missed and an additional $180 in annual household income if employed, and a 2-percentage-point decline in the odds of receiving supplemental security income for disability. All estimates are statistically significant at the 0.05 level.
  
  
  CONCLUSIONS
  Using a large, representative sample of non-institutionalized adults in the U.S., we find that physical activity limitations are associated with worse economic outcomes across multiple economic metrics. Combined with estimates of improved functional ability following knee and hip surgery, we quantify some of the economic benefits of surgery for arthritis of the knee and hip. This information helps improve understanding of the societal benefits of medical treatment for musculoskeletal conditions.
authors.affiliation: IHS Global Inc,, 1150 Connecticut Ave,, NW, Suite 401, Washington, DC, 20036, USA. tim.dall@ihs.com.
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Dall
authors.forename: Paul
authors.initials: P
authors.lastname: Gallo
authors.forename: Lane
authors.initials: L
authors.lastname: Koenig
authors.forename: Qian
authors.initials: Q
authors.lastname: Gu
authors.forename: David
authors.initials: D
authors.lastname: Ruiz