Elsevier

Mayo Clinic Proceedings

Volume 89, Issue 8, August 2014, Pages 1072-1079
Mayo Clinic Proceedings

Original article
Body Composition and Mortality in a Large Cohort With Preserved Ejection Fraction: Untangling the Obesity Paradox

Data Previously Presented: These data were presented in part at the American College of Cardiology Annual Scientific Sessions on March 2012 in Chicago, IL, and in part at the American Heart Association Annual Scientific Sessions on November 2012 in Los Angeles, CA.
https://doi.org/10.1016/j.mayocp.2014.04.025Get rights and content

Abstract

Objective

To evaluate the effects of body composition as a function of lean mass index (LMI) and body fat (BF) on the correlation between increasing body mass index (BMI; calculated as the weight in kilograms divided by the height in meters squared) and decreasing mortality, which is known as the obesity paradox.

Patients and Methods

We retrospectively assessed 47,866 patients with preserved left ventricular ejection fraction (≥50%). We calculated BF by using the Jackson-Pollock equation and LMI using (1 − BF) × BMI. The population was divided according to the sex-adjusted BMI classification, sex-adjusted LMI classification, and sex-adjusted BF tertiles. The population was analyzed by using multivariate analysis for total mortality over a mean follow-up duration of 3.1 years by using the National Death Index, adjusting for left ventricular ejection fraction, left ventricular mass index, age, sex, and relative wall thickness.

Results

In the entire population, higher BMI was narrowly associated (hazard ratio [HR], 0.99; P<.001) with lower mortality. The higher LMI group was clearly protective (HR, 0.71; P<.001), whereas BF tertile was associated with lower mortality only if no adjustment was made for LMI (HR, 0.87; P<.001 without LMI; HR, 0.97; P=.23 with LMI). In the lean patients, low BMI was clearly associated with higher mortality (HR, 0.92; P<.001) and lower BF tertile was associated with lower mortality only if no adjustment was made for LMI (HR, 0.80; P<.001 without LMI; HR, 1.01; P=.83 with LMI). The underweight patients stratified by BF seemed to have an increased mortality (HR, 1.91; 95% CI, 1.56-2.34) that was independent of LMI. However, in obese patients, both BMI (HR, 1.03; P<.001) and BF (HR, 1.18; P=.003) were associated with higher mortality, even after adjusting for LMI, which remained protective (HR, 0.57; P<.001) independently of BF.

Conclusion

Body composition could explain the inverse J shape of the mortality curve noted with increasing BMI. Body fat seems to be protective in this cohort only if no adjustment was made for LMI, although being underweight stratified by BF seems to be an independent risk factor. Lean mass index seems to remain protective in obese patients even when BMI is not.

Section snippets

Study Design

The study was based on relevant demographic, clinical, and echocardiographic data from a clinical echocardiographic report database that were recorded at the Ochsner Medical Center (New Orleans, Louisiana) between October 7, 1997, and November 20, 2002. We specifically evaluated patients with preserved systolic function (defined as left ventricular ejection fraction [LVEF] ≥50%) who were US residents, resulting in 47,865 studies. Survival was determined by using the National Death Index during

Baseline Characteristics

The study population consisted of 47,865 patients (21,568 obese patients [55%]), 45% of whom were men. The mean age of the cohort was 62±15.4 years. According to the BMI (29±7 kg/m2), patients were overweight, and the mean LMI was 18±3 kg/m2. The mean follow-up time was 633 days. Mortality in the course of this study was 7.6% for the total population (Table 1). When stratified by obesity defined by BMI, the obese population of the cohort reported significantly higher blood pressure, BF, and

Discussion

There were several important findings in this study. First, we confirmed the presence of a U-shaped BMI-mortality curve in this population, in which the lowest adjusted mortality was found in the mildly obese (Figure 1). Second, we found a survival benefit associated with high LMI that was independent of any effect of BF and was present in the lean and the obese population (Table 2). Third, we found a protective effect associated with BF in the overall population and, more specifically, the

Conclusion

Body composition plays a critical role in the obesity paradox. Whenever examining a potential protective effect of BF, LMI should be considered. At higher BMI, BF is associated with an increase in mortality.

References (34)

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