A study published in The Spine Journal in April 2020 titled ”Obesity negatively affects cost efficiency and outcomes following adult spinal deformity surgery” investigated the intricacies of the cost difference for adult spinal deformity (ASD) correction surgery in obese and nonobese patients. The group used Medicare reimbursement claims and PearlDiver to identify patients and expenses for ASD surgery at a single institution over a 5-year span. They determined the average cost of surgery, cost of a quality adjusted life year (QALY), and a QALY discounted through a patient’s life expectancy.
They found that the average cost of surgery was more than 8% higher for the most obese patients compared to normal weight individuals, and the cost of a QALY for obese patients was 32% higher than nonobese patients at $331,048. Revision rates were also significantly higher for obese patients. When considering the cost per QALY at life expectancy the difference is even greater with 47.5% greater cost for obese versus nonobese. However, for all patients, the cost per QALY at life expectancy was below $30,000, which is well under the generally accepted thresholds of cost per QALY to rationalize a treatment.
An interesting trend appeared in the data showing a decreasing cost per QALY at life expectancy for increasingly obese patients. For obesity I, II, and III the costs were approximately $27,500, $18,300, and $9,600, respectively. The authors explain that this counterintuitive trend was primarily due to the starting quality of life measures on the EQ-5D survey. All three groups had similar postoperative EQ-5D scores, but the most obese had substantially lower preoperative scores, resulting in significantly greater improvement.
Some potential compounding factors that were not addressed by the authors include patient co-morbidities and adjustments to life expectancy for each group. It is not clear if selection criteria for other health status indicators and comorbidities were consistent across all BMI classes, potentially biasing the most obese patients toward fewer additional comorbidities than other groups. Additionally, the life expectancy used to calculate QALY was not adjusted for each BMI class. It is well documented that higher BMI is associated with reduced life expectancy.
Overall, the study shows that obesity results in significantly higher surgical costs and costs per QALY, but the costs are still rationalizable to healthcare payers.
