Moral Hazard and Less Invasive Medical Treatment for Coronary Artery Disease: An Analysis of Smoking in the National Health Interview Survey

We use Medicare claims data linked to the National Health Interview Survey (NHIS) to study how changes in patient smoking behavior are related to three common treatments for Coronary Artery Disease (CAD): medical management (MM), Percutaneous Coronary Intervention (PCI), and Coronary Artery Bypass Graft (CABG).  We find that the more invasive a patient’s treatment, the more likely he is to quit smoking.  Patients undergoing CABG, the most invasive procedure, are 13 and 16 percentage points more likely to quit smoking than patients treated with PCI or medical management, respectively, in the one-year window surrounding their procedure.  These results emerge from a discrete time linear probability hazard model. We include only individuals who smoke 9.5 years before treatment or diagnosis.  Individuals who smoke in all periods are the censored observations. The first period is defined by the window starting 9.5 years before treatment and ending 8.5 years before treatment. The last period is the window from 0.5 years after treatment to 1.5 years after treatment.  The key window is period 10 and spans the dates from half a year before treatment or diagnosis to half a year after.  We control for an indicator for whether the patient had an acute myocardial infarction, indicators for 29 Elixhauser comorbidity conditons, and an indicator for whether a PCI or a CABG patient was diagnosed with CAD at least six months prior to surgery.  We also control for demographic and socioeconomic characteristics.  Our study is motivated by prior economic research on moral hazard, showing that individuals change their behavior when their perceived risks change.  The behavioral response that we observe may be accompanied by such similar responses as reductions in excessive alcohol consumption, improvements in diet, or increases in exercise.  These responses may partially offset the risks inherent to a more invasive procedure and help explain why the longer term outcomes for CABG patients rival or even exceed those of similar patients receiving PCI or medical management.