Economic implications of obesity among people with atherothrombotic disease.

Objective: The purpose of this study was to ascertain the impact of obesity on the cost of disease management in people with or at high risk of atherothrombotic disease from a governmental perspective using a bottom-up approach to cost estimation. In addition, the aim was also to explore the causes of any differences found.
Method: The health-care costs of obesity were estimated from 2819 participants recruited into the nationwide Australian REACH Registry with established atherothrombotic disease or at least three risk factors for atherothrombosis. Enrollment was in 2004, through primary care general practices. Information was collected on the use of cardiovascular drugs, hospitalizations and ambulatory care services. 'Bottom-up' costing was undertaken by assigning unit costs to each health-care item, based on Australian Government-reimbursed figures 2006-2007. Linear-mixed models were used to estimate associations between direct medical costs and body mass index (BMI) categories.
Results: Annual pharmaceutical costs per person increased with increasing BMI category, even after adjusting for gender, age, living place, formal education, smoking status, hypertension and diabetes. Adjusted annual pharmaceutical costs of overweight and obese participants were higher ($7 (P=0.004) and $144 (<0.001), respectively) than those of the normal weight participants. This was due to participants in higher BMI categories receiving more pharmaceuticals than normal weight participants. There was no significant change across the BMI categories in annual ambulatory care costs and annual hospital costs.
Conclusion: In these participants with or at high risk of atherothrombotic disease, annual pharmaceutical costs were greater in participants of higher BMI category, but there was not such a gradient in the annual hospital or ambulatory care costs. The greater cardiovascular pharmaceutical costs for participants of higher BMI categories remained even after adjusting for a range of demographic factors and comorbidities. Our results suggest that these costs are explained by the higher number of drugs used among people with atherothrombotic disease. Further investigation is needed to understand the reasons for this level of drug use.