Direct per-person costs attributable to AORC were estimated using a series of four-stage regression analyses6 that modeled the probability and magnitude of medical care expenditures among adults aged ≥18 years. This modeling included adjustment for the following variables: age (18-44, 45-64, or ≥65 years), sex, race (white or nonwhite), ethnicity (Hispanic or non-Hispanic), marital status (single, currently married, widowed, separated, or divorced), highest educational attainment (less than high school, high school graduate, some college, college graduate, or graduate school), health-insurance status (no insurance, public insurance only, or any private insurance), and the presence of nine other high-cost chronic conditions (hypertension, other forms of heart disease, pulmonary disease, stroke, other neurologic conditions, diabetes, cancer, mental illness, or non-AORC musculoskeletal conditions). The average per-person direct cost attributable to AORC was the difference between the observed and corresponding expected medical costs. Expected costs simulated costs among persons with AORC as if they did not have AORC.2 Average per-person direct costs were generated for overall expenditures and for each of the following four cost categories: (1) ambulatory care, (2) emergency department and inpatient services, (3) prescriptions, and (4) other costs (i.e., home health care, vision aids, dental visits, and medical devices). Finally, total national direct costs were calculated as the product of the number of persons aged ≥18 years reporting AORC and the average per-person direct costs.