Obesity and heart failure: when 'epidemics' collide.

Abstract

The growing burden of obesity has been referred to as an ‘epidemic’. The World Health Organization estimates that 50% of adults living in Europe are overweight or obese, a population approximately equivalent to that of Germany, France, the UK, and Italy put together. This concerning statistic is made more terrifying by the data presented by Rosengren et al. in this issue of the journal. They examined the association between body weight mass and the development of heart failure in >1.5 million young men (mean age 18.6 years). They report that the incidence of heart failure in these young men, who had their body mass index (BMI) calculated as part of the physical examination for national service, was 5–7 per 100 000 person-years of follow-up in those of normal weight, rising to 12–40 per 100 000 person-years of follow-up in those who were overweight or obese as defined by their BMI. The risk of developing heart failure was nine times higher in the highest BMI category ( 35 kg/m) compared with those with normal BMI even after adjustment. Behind this relatively simple (and perhaps unsurprising) message lies a complex story that underscores the difficulty we have in dealing with the obesity epidemic. Compared with those who were normal weight, in those who were obese, the relative risk of developing heart failure was higher than the risk of experiencing a myocardial infarction (MI) or stroke. This suggests that there may be a closer association between BMI and heart failure than either stroke or MI. Given that heart failure is commonly caused by ischaemic heart disease, this finding is somewhat counterintuitive. We might expect BMI to be more strongly linked to the most common precursor of heart failure, atherosclerotic heart disease, than heart failure itself. Obesity is associated with diabetes, high cholesterol, and inflammation, all risk factors for the development of atherosclerosis. However, there is evidence linking obesity directly to heart failure. Obesity has a number of effects on the cardiovascular system (Figure 1). Many of these are direct effects on the myocardium and are linked to the development of heart failure. Left ventricular mass and left atrial volume increase with increasing BMI, as does the degree of diastolic and systolic dysfunction, and ongoing myocardial injury may be detectable with newer high sensitivity troponin assays. Higher BMI is also associated with higher cardiac output, increased blood volume, and alterations in pressure–volume relationships in the heart that deal with these changes. Activation of various inflammatory pathways may explain some of the relationship between obesity and heart failure. Finally, cardiac steatosis is a recognized complication of obesity. Deposition of fat in the myocardium leads to progressive fibrosis, further altering cardiac function. Contrast this to the associations between obesity and ischaemic heart disease which are less direct (Figure 1). Although not all atherosclerotic disease culminates in a myocardial infarction, autopsy findings of young military personnel confirm that increasing BMI is associated with a greater burden of atherosclerosis. Therefore, despite the evidence linking obesity directly to the development of heart failure, could the association between obesity and heart failure simply be confounded by ischaemic heart disease? In the analysis by Rosengren et al., subgroup and secondary analyses were used to explore this issue. The association between BMI and heart failure was examined according to the aetiology of heart failure. The risk of heart failure with a secondary diagnosis of coronary heart disease, hypertension, or diabetes mellitus was higher than the risk of heart failure without any of these diagnoses. For every one unit increase in BMI, the risk of heart failure, that occurred with coronary heart disease, diabetes, or hypertension was 1.21 [95% confidence interval (CI) 1.19–1.22]. Although this was stronger than the association between BMI and heart failure due to cardiomyopathy, i.e. heart failure without an obvious aetiology and intermediary pathway, [hazard ratio (HR) 1.11, 95% CI 1.08–1.14], the population-attributable fraction for obesity and heart failure due to cardiomyopathy was 15.4%, suggesting that the direct link between obesity and the development of heart failure is a substantial issue at a population level. However, we must be careful when trying to draw conclusions from these data, no matter how careful the analyses. The competing risk of death was not taken into account, nor was the occurrence of

DOI: 10.1093/eurheartj/ehw357

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Cite this paper

@article{Jhund2017ObesityAH, title={Obesity and heart failure: when 'epidemics' collide.}, author={Pardeep S . Jhund}, journal={European heart journal}, year={2017}, volume={38 24}, pages={1934-1936} }