Relation of body mass index to outcomes in acute coronary syndrome

We assessed the association of BMI with all-cause and cardiovascular (CV) mortality in a contemporary acute coronary syndrome cohort. Patients from the Australian Cooperative National Registry of Acute Coronary Care, Guideline Adherence and Clinical Events and Global Registry of Acute Coronary Events between 2009 and 2019, were divided into BMI subgroups (underweight: <18.5, healthy: 18.5 to 24.9, overweight: 25 to 29.9, obese: 30 to 39.9, extremely obese: >40). Logistic regression was used to determine the association between BMI group and outcomes of all cause and CV death in hospital, and at 6 months. 8,503 patients were identified, mean age 64 ± 13, 72% male. The BMI breakdown was: underweight- 95, healthy- 2,140, overweight- 3,258, obese- 2,653, extremely obese- 357. Obese patients were younger (66 ± 12 vs 67 ± 13), with more hypertension, diabetes, and dyslipidemia vs healthy (all p < 0.05). Obese had lower hospital mortality than healthy: all-cause: 1% versus 4%, aOR (95% CI): 0.49(0.27, 0.87); CV: 1% versus 3%, 0.51(0.27, 0.96). At 6-month underweight had higher mortality than healthy: all-cause: 11% versus 4%, 2.69(1.26, 5.76); CV: 7% versus 1%, 3.54(1.19, 10.54); whereas obese had lower mortality: all-cause: 1% versus 4%, 0.48(0.29, 0.77); CV: 0.4% versus 1%, 0.42(0.19, 0.93). When BMI was plotted as a continuous variable against outcome a U-shaped relationship was demonstrated, with highest event rates in the most obese (>60). In conclusion, BMI is associated with mortality following an acute coronary syndrome. Obese patients had the best outcomes, suggesting persistence of the obesity paradox. However, there was a threshold effect, and favorable outcomes did not extend to the most obese.