Are Lifestyle Interventions in Primary Care Cost-Effective? : An Analysis Based on a Markov Model, Differences-In-Differences Approach and the Swedish Björknäs Study

Background: Lifestyle interventions affect patients' risk factors for metabolic syndrome (MeSy), a pre-stage to cardiovascular diseases, diabetes and related complications. An effective lifestyle intervention is the Swedish Bjorknas intervention, a 3-year randomized controlled trial in primary care for MeSy patients. To include future disease-related cost and health consequences in a cost-effectiveness analysis, a simulation model was used to estimate the short-term (3-year) and long-term (lifelong) cost-effectiveness of the Bjorknas study. Methodology/Principal Findings: A Markov micro-simulation model was used to predict the cost and quality-adjusted life years (QALYs) for MeSy-related diseases based on ten risk factors. Model inputs were levels of individual risk factors at baseline and at the third year. The model estimated short-term and long-term costs and QALYs for the intervention and control groups. The cost-effectiveness of the intervention was assessed using differences-in-differences approach to compare the changes between the groups in the health care and societal perspectives, using a 3% discount rate. A 95% confidence interval (CI), based on bootstrapping, and sensitivity analyses describe the uncertainty in the estimates. In the short-term, costs are predicted to increase over time in both groups, but less in the intervention group, resulting in an average cost saving/reduction of US$-700 (in 2012, US $ 1= six point five seven SEK) and US$-500, in the societal and health care perspectives. The long-term estimate also predicts increased costs, but considerably less in the intervention group: US$-7,300 (95% CI: US$-19,700 to US $-1,000) in the societal, and US$-1,500 (95% CI: US$-5,400 to US$ 2,650) in the health care perspective. As intervention costs were US$ 211 per participant, the intervention would result in cost saving. Furthermore, in the long-term an estimated 0.46 QALYs (95% CI: 0.12 to 0.69) per participant would be gained. Conclusions/Signi