Some studies have suggested a lower mortality in obese subjects with cardiovascular disease. The aim of this study was to evaluate the relationship between body mass index (BMI) and outcomes in patients with acute coronary syndrome (ACS).

The study included 13,742 patients undergoing coronary angiography for ACS between 2012 and 2016 from the All New Zealand Acute Coronary Syndrome–Quality Improvement (ANZACS-QI) registry. Patients were categorised by BMI (kg/m²) as: underweight <18.5, normal 18.5 to <25, overweight 25 to <30, mildly obese 30 to <35, moderately obese 35 to <40, and severely obese ≥40. The primary endpoint of the study was all cause mortality with secondary endpoints of cardiovascular disease (CVD) and non-CVD mortality within 4 years of discharge.

Unadjusted all cause mortality was lowest in the mildly obese but no different to normal or overweight after adjustment for multiple confounders. Adjusted all cause mortality was higher in the moderately (hazard ratio [HR] 1.39, 95% CI: 1.10–1.75) and severely obese (2.06, 95% CI: 1.57–2.70) compared to the mildly obese. Non-CVD mortality (HR 1.58, 95% CI: 1.12–2.23) was the major contributor to higher all cause mortality in moderately obese patients. Both CVD mortality (HR 2.36, 95% CI: 1.67–3.32) and non-CVD mortality (HR 1.67, 95% CI: 1.07–2.61) contributed to higher all cause mortality in the severely obese.

Moderate and severe obesity is associated with worse survival post ACS influenced by higher non-CVD mortality in moderate/severe obesity and higher CVD mortality in severe obesity.