Health insurance claims data as a means of assessing reduction in co-morbidities 6 months after bariatric surgery

Background: We measured the very short-term change in obesity-related co-morbidities following bariatric surgery. Methods: Claims data were analyzed for 933 patients aged 18-62 who were covered by one of 11 New York State health plans and underwent bariatric surgery during calendar year 2002. Data covered 6 months before to 6 months after surgery. Logit regression and fixed effects logit regressions were estimated, to analyze change in the following co-morbidities after bariatric surgery: diabetes, hyperlipidemia, hypertension, asthma, sleep apnea, degenerative joint disease, gastroesophageal reflux, and depression. Results: There were statistically significant post-surgery decreases in each outcome studied. Controlling for individual fixed effects, the probability of a diabetes diagnosis fell by 20% after bariatric surgery. The probability of sleep apnea fell by 33%, and the probability of the other obesity-related co-morbidities fell by 11 to 19% at 6 months. Conclusion: Claims data are useful for assessing changes in a wide range of co-morbidities following bariatric surgery. The data indicate significant decreases in obesity-related co-morbidities after bariatric surgery, although considerably smaller than those found in previous studies, which underscores the need for randomized controlled trials of bariatric surgery. Limitations of this study include: follow-up only at 6 months, nonexperimental data, and an unknown degree of underreporting of co-morbidities in claims data.