Obesity and cardiovascular risks : a systematic review of current evidence

Abstract

Introduction: Obesity is a growing global epidemic and its burden on the public health system is increasingly recognized. The population attributable risk of obesity in coronary heart disease in Hong Kong was quoted to be 9.2%. Recent data suggested an improved prognosis in overweight and obese patients with acute myocardial infarction and acute decompensated heart failure. The term “obesity paradox” was coined to describe this phenomenon. This review systematically evaluated current evidence and explored the relationship between obesity and cardiovascular disease.

Methods: A systematic review of articles associating obesity with cardiovascular disease was performed. Total number of obesity-related cardiovascular disease was determined using a priori knowledge and a subsequent search of PubMed using medical subject headings (MeSH) and Boolean. Relevant articles for each individual cardiovascular disease were retrieved. The title and abstract of the retrieved articles were screened, and relevant articles were included for evaluation of quality using a modified version of the Grading of Recommendations Assessment, Development and Evaluation (GRADE). Qualitative analyses and meta-analyses were performed for cardiovascular conditions in which obesity paradox was observed.

Results: A total of 12 obesity-related cardiovascular diseases was identified. One hundred and eight-six articles relevant to these 12 conditions were reviewed in detail and 147 articles were included for assignment to a GRADE-observational category. The condition with the greatest number of high quality articles (i.e. GRADE of 4) was incident heart failure (n=9), followed by hypertension (n=7), myocardial ischemia / coronary artery disease (n=6), atrial fibrillation and stroke (n=5 for both), angina pectoris and sudden cardiac death (n=2 for both) and left atrial enlargement (n=1). The best evidence was only of moderate quality (i.e. GRADE of 3) in left ventricular hypertrophy (n=2) and implantable cardioverter defibrillator complications (n=1). Only low quality evidence (i.e. GRADE 2) were available for both left ventricular dilatation (n=1) and diastolic dysfunction (n=3). Overall, obesity was associated with higher risk for all cardiovascular diseases. Mortality rates in heart failure, myocardial ischemia / coronary artery disease and stroke were lower in overweight and mildly obese individuals as compared to normal weight controls, but the relationship did not reach statistical significance on meta-analysis. Conclusions: This review of current evidence suggests that obesity is associated with increased risks for development of cardiovascular disease, but once the cardiovascular disease is established, there is some evidence to suggest better prognosis in association in higher BMI. Biological and statistical explanation for the “obesity paradox” was explored.