Obesity paradox in patients with non‐ST‐elevation myocardial infarction undergoing percutaneous coronary intervention: A nationwide retrospective observational study

The prevalence of obesity in the United States is high, with over 35% of the population classified as obese. Obesity, along with the lifestyle factors contributing to it, is considered a major risk factor for heart disease. However, research studies have reported controversial findings regarding its impact on morbidity and mortality. Data was obtained from the Nationwide Inpatient Sample database from January 2016 to December 2020. The study included adult patients with a principal discharge diagnosis of NSTEMI who underwent PCI during hospitalization. They were divided into obese (BMI > 30) and not obese (BMI < 30). The primary outcome was inpatient mortality. Secondary outcomes were cardiogenic shock, cardiac arrest, arrhythmias, and acute renal failure, as well as the need for transfusions, pressors, ventilators, and ECMO. We analyzed 448,424 hospitalizations for NSTEMI, of which 172,665 patients underwent PCI. Among these, 39,548 (22.9%) were obese (BMI >30). Obesity was associated with lower in-hospital mortality compared to non-obese patients (1.2% vs. 1.8%; adjusted odds ratio [aOR]: 0.82; 95% CI: 0.74–0.90; p < 0.001), after adjustment for age, sex, race, and Charlson Comorbidity Index. Obese patients also had lower rates of cardiogenic shock (2.7% vs. 3.3%; aOR: 0.84; 95% CI: 0.78–0.90; p < 0.001), cardiac arrest (1.3% vs. 1.6%; aOR: 0.86; 95% CI: 0.78–0.95; p < 0.005), and ventricular arrhythmias (5.2% vs. 5.7%; aOR: 0.93; 95% CI: 0.88–0.98; p < 0.005). They also required fewer blood transfusions (1.9% vs. 2.3%; aOR: 0.90; 95% CI: 0.83–0.98; p < 0.05) and mechanical ventilation (2.9% vs. 3.2%; aOR: 0.91; 95% CI: 0.85–0.98; p < 0.05). No significant differences were observed in dialysis, vasopressor use, or ECMO. However, obese patients had higher rates of acute kidney injury (15.0% vs. 13.5%; aOR: 1.25; 95% CI: 1.21–1.29; p < 0.001) and acute respiratory failure (9.1% vs. 8.2%; aOR: 1.17; 95% CI: 1.13–1.23; p < 0.001). The “obesity paradox” suggests that despite obesity's role in cardiovascular disease risk, individuals with obesity may have a survival advantage during acute cardiovascular events and certain surgeries. Our study aligns with these findings, underscoring the need for further research to comprehend the underlying pathophysiological mechanisms.