Obesity Paradox in the Intrahospital and Follow-Up Phases of the Acute Coronary Syndrome: A Meta-Analysis and Systematic Review

BACKGROUND: Obesity is an important risk factor for the development of dyslipidemia, diabetes mellitus, hypertension, coronary artery disease, ventricular dysfunction, congestive heart failure (HF), stroke, and cardiac arrhythmias. OBJECTIVES: This meta-analysis brings comprehensive evaluation about still controversial association between the body mass index (BMI) and the outcomes of acute coronary syndrome. METHOD: PubMed/ScienceDirect databases were systematically searched for studies with baseline parameters, primary (HF, cardiogenic shock, cardiac arrest, reinfarction, stroke, death, total in-hospital complications) and secondary outcomes (reinfarction, stroke, death, total major adverse cardiovascular events [MACE]) in relation to BMI strictly classified into four groups (underweight [<18.5 kg/m2], normal weight [18.5-24.9 kg/m2], overweight [25.0-29.9 kg/m2], and obese [≥30.0 kg/m2], grouped into mildly obese [30.0-34.9 kg/m2] and severely obese [≥35.0 kg/m2]). RESULTS: We included 24 studies, with 585,919 participants (55.5% males), aged 66.8 years. Underweight was negatively associated with hypertension, hyperlipidemia and diabetes, and positively with primary outcomes {HF (odds ratio [OR] = 1.37, confidence interval [CI] [1.15-1.63]), cardiogenic shock (OR = 1.43, CI [1.04-1.98]), stroke (OR = 1.21, CI [1.05-1.40]), overall death (OR = 1.64, CI [1.20-2.26]), total in-hospital complications (OR = 1.39, CI [1.24-1.56])} and secondary outcomes during 34-month follow-up {cardiovascular/overall death (OR = 3.78, CI [1.69-8.49]/OR = 2.82, CI [2.29-3.49]), respectively, total MACE (OR = 2.77, CI [2.30-3.34])} (for all p < 0.05). Obesity had positive association with hypertension, hyperlipidemia, diabetes and smoking, and negative with primary outcomes {reinfarction (OR = 0.83, CI [0.76-0.91]), stroke (OR = 0.67, CI [0.54-0.85]), overall death (OR = 0.55, CI [0.49-0.63]), total in-hospital complications (OR = 0.81, CI [0.70-0.93])} and secondary outcomes {cardiovascular/overall death (OR = 0.77, CI [0.66-0.88]/OR = 0.62, CI [0.53-0.72]), respectively, total MACE (OR = 0.63, CI [0.60-0.77])} (for all p < 0.05). This negative association with several primary outcomes (cardiogenic shock, overall death, total in-hospital complications) and secondary outcomes (cardiovascular/overall death, total MACE) was more pronounced in mild obesity (p < 0.05). These results give an "obesity paradox" with a bimodal pattern (slightly U-shaped). CONCLUSIONS: Obesity is positively associated with traditional cardiovascular risk factors and negatively with primary and secondary outcomes, which confirms the persistence of overall "obesity paradox."