Obesity Paradox in Peripheral Arterial Disease: Results of a Propensity Match Analysis from the National Inpatient Sample

Introduction The role of obesity in cardiovascular mortality is controversial. The obesity paradox has been widely attributed to smoking in the underweight. Large-scale studies analyzing the outcomes of peripheral arterial disease (PAD) in patients with a higher body mass index (BMI) while accounting for confounders such as smoking are lacking. Method The 2016 National Inpatient Sample (NIS) was used to identify all admissions with a primary discharge diagnosis of PAD. A secondary diagnosis of obesity or elevated BMI was used to segregate the admissions into two groups. Propensity scores were calculated to match and control both groups for age, smoking, and diabetes, amongst other confounders. A multivariate logistic and linear regression analysis was performed to calculate the odds ratio for in-hospital mortality, amputation, need for intervention (angioplasty or bypass), acute kidney injury, hospital charges, and length of stay. Non-obesity-related PAD admissions were selected as the reference groups. Results Among 248,288 PAD-related admissions, 41,618 had a secondary diagnosis of obesity. After calculating propensity scores for 1-1 matching, 41,589 admissions in the PAD and obesity group were compared to a similar number of admissions in the reference population. Patients with a concomitant diagnosis of obesity had lower odds of amputation (OR=0.90, 95% CI=0.84-0.95, p<0.001), need for intervention (OR=0.66, 95% CI=0.62-0.69, p<0.0001), and in-hospital mortality (OR=0.81, 95% CI=0.74-0.87, p<0.0001). On the contrary, the odds of having acute kidney injury were higher with elevated BMI (OR=1.30, 95% CI=1.26-1.34, p<0.0001). Conclusion Despite increasing the risk of hypertension, diabetes, and hypertriglyceridemia, the obesity paradox continues to exist with a better short-term prognosis in patients with PAD. Future studies looking into the pathophysiology behind this phenomenon are needed.