A group of Queen’s University researchers has revealed that overweight and obese patients had lower average health-care costs, as well as lower mortality and fewer adverse outcomes after cardiac surgery compared with normal weight, morbidly obese and particularly underweight patients, based on body mass index (BMI).

“These results may impact health resource planning, shifting the focus to underweight and morbidly obese patients prior to, during and after cardiac surgery to improve their outcomes,” says Ana Johnson (Public Health Sciences, Institute for Clinical Evaluative Sciences).

The researchers determined obesity actually has a protective effect.

“This is what is referred to as the obesity paradox,” says Joel Parlow (Anesthesiology and Perioperative Medicine). “The paradox implies that even though obesity is a clear risk factor for the development of heart disease, moderately obese patients actually do better when they require heart surgery. We can’t say definitively why this is the case, but one factor may be that lower weight people have reduced nutritional reserves that are required for healing, while morbidly obese patients are predisposed to a variety of adverse outcomes.”

Drs. Parlow, Johnson and Brian Milne (Anesthesiology and Perioperative Medicine) analyzed the economic costs incurred in more than 50,000 cardiac surgery patients in Ontario during their hospital admission, and for the first year following surgery. They found that although heart surgery in overweight and moderately obese patients costs significantly less on average, the preponderance of these same groups requiring heart surgery in the first place leads to far higher annual costs to the health-care system related to obesity.

As a follow-up to this research project, Drs. Parlow, Johnson and Milne are working to develop a model that will predict the financial resources needed for cardiac surgery based on the patient’s BMI group. They are also looking to develop a clear definition of healthy body weight, which may differ depending on the clinical situation.

The research was published in the European Journal of Health Economics.