The Impact of Obesity on Risk Factors and Prevalence and Prognosis of Coronary Heart Disease—The Obesity Paradox
Section snippets
Obesity and Coronary Heart Disease (CHD) in primary prevention
Obesity is an increasing public health problem in the United States (US) and much of the developed world. Being overweight is defined by National Institutes of Health as a body mass index (BMI) ≥ 25 kg/m2 and obesity as a BMI ≥ 30 kg/m2. By these criteria, in 1960 approximately one in every ten Americans was obese, a number which has since tripled.1 At the same time the proportion of the population which was overweight remained constant; currently the majority of the population is overweight or
BMI paradox or obesity paradox
The obesity paradox has been most commonly described defining obesity by BMI, since it is a readily measured parameter in clinical practice. While the presentation of the CHD patient varies, the BMI–mortality curve is typically U-shaped, with increasing mortality at the extremes of obesity.24 This relationship has been confirmed in many studies from all over the world,25 with varying results in terms of optimal and most detrimental BMI range. In a large meta-analysis of 40 cohort studies by
Impact of presentation
The BMI paradox has repeatedly been shown in registries of hospitalized patients. The above mentioned analysis of Dhoot et al.27 was done in an in-hospital group of 400,000 patients presenting with both STEMI and non-STEMI in 2009. Fonarow et al.51 evaluated in-hospital mortality in the Acute Decompensated Heart Failure National Registry and found a decrease of 10% mortality after adjustment for confounders associated with every 5 unit increase in BMI.
In the population referred for
Impact of CRF
Increasing evidence points towards a significant interaction between CRF and the obesity paradox. CRF is a powerful prognostic factor in CHD and other diseases, and it has even been suggested that its improvement might yield greater health benefits than a change in weight.59 In several studies now in CHD60 and HF,61 the obesity paradox by BMI and other measures of obesity has been shown to be predominantly present in individuals with low CRF. In a recent study of 2066 patients with systolic HF
Mechanisms
The obesity paradox could be associated with several biases such as a lead time bias, confounding bias and publication bias. A lead time bias occurs when earlier detection of the disease is confused with prolonged survival. The increase in pretest probability for CHD in obese individuals could lead to earlier testing, and earlier diagnosis could result in increased survival. In contrast, lean individuals have a lower pretest probability, and consequently present with more advanced disease, and
Conclusions
Despite the known adverse effects of obesity on the development, severity and progression, it has repeatedly been shown that CHD patients with overweight or obese BMI and even BF have lower mortality, especially in combination with low CRF. Intentional weight loss remains protective and a goal in CHD patients. Above all, higher levels of CRF are associated with better prognosis in all populations of CHD and CV patients, and in most studies, an obesity paradox in not apparent in patients with
Statement of Conflict of Interest
The authors declare that there are no conflicts of interest.
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Statement of conflict of interest: see page 406.