Using the MAXNHANES Merged Data to Evaluate the Association of Obesity and Medicaid Costs

This brief presents the results of the first study conducted using the newly merged Medicaid Analytic eXtract (MAX) and National Health and Nutrition Examination Survey (NHANES) data. The study evaluated the association between Medicaid costs and obesity among adults in 1999–2004. Although the estimated costs were higher for obese adults than for non-obese adults, the combination of a small sample size for NHANES data, wide variation in costs among Medicaid enrollees, and the necessity of controlling for state variation yielded an unstable model with imprecisely estimated relationships. The results demonstrate the hazard of using a small national survey (NHANES) with a state-based data system (MAX) to perform cost analyses, particularly when the range of realistic costs is large.