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Impact of BMI on Heart Failure Mortality
Study Questions:
What is the influence of race/ethnicity on the relationship between body mass index (BMI) and mortality in heart failure with preserved ejection fraction (HFpEF) and HF with reduced EF (HFrEF) patients?
Methods:
The authors utilized Get With The Guidelines–Heart Failure (GWTG–HF) registry data to assess the relationship between BMI and in-hospital mortality by using logistic regression modeling. They used a multivariate model adjusted for patient and hospital characteristics, including age, gender, medical history (anemia, ischemic history, cerebrovascular accident/transient ischemic attack, diabetes, hyperlipidemia, hypertension, chronic obstructive pulmonary disease or asthma, peripheral vascular disease, renal insufficiency, smoking), admission vital signs and laboratory test results (systolic blood pressure, heart rate, and sodium and blood urea nitrogen concentrations), hospital region, and academic status and number of beds. The 30-day and 1-year mortality rates were evaluated from discharge date to 30 days and 1 year afterward using Cox regression modeling. For 30-day and 1-year mortality rates, the BMI knot point was 30 kg/m2. Restricted cubic spline relationships were plotted for 30-day mortality.
Results:
The final study cohort was comprised of 39,647 HF patients including (32,434 [81.8%] white subjects; 3,809 [9.6%] black subjects; 1,928 [4.9%] Hispanic subjects; 544 [1.4%] Asian subjects; and 932 [2.3%] other subjects); 59.7% of subjects had HFpEF, and 30.7% were obese. More black and Hispanic patients had Class I or higher obesity (BMI ≥30 kg/m2) than whites, Asians, or other racial/ethnic groups (p < 0.0001). Among subjects with HFpEF, higher BMI was associated with lower 30-day mortality, up to 30 kg/m2 with a small risk increase above 30 kg/m2 (BMI: 30 vs. 18.5 kg/m2), and hazard ratio (HR) of 0.63 (95% confidence interval [CI], 0.54-0.73). For BMI >30 kg/m2, each 1-U increase in BMI was associated with a 2% greater odds of in-hospital death for patients with HFpEF (odds ratio [OR], 1.02; 95% CI, 1.01-1.04). A modest relationship was observed in HFrEF subjects (BMI: 30 vs. 18.5 kg/m2; HR, 0.73; 95% CI, 0.60-0.89), with no risk increase above 30 kg/m2. Among patients with HFrEF, each BMI unit increase up to 25 kg/m2 was associated with 5% lower odds of in-hospital death (OR, 0.95; 95% CI, 0.91-0.99). Above a BMI of 25 kg/m2, each 1-U BMI increase was associated with 4% higher odds of in-hospital death (OR, 1.04; 95% CI, 1.03-1.05). There were no significant interactions between BMI and race or ethnicity related to 30-day mortality (p > 0.05).
Conclusions:
The authors concluded that their data suggest that the obesity paradox for 30-day mortality exists at all BMI levels in HFrEF, but not in patients with HFpEF. Higher BMI was associated with lower 30-day mortality across racial/ethnic groups in a manner not consistent with the J-shaped relationship noted for coronary artery disease. The authors suggested that the differential slope of obesity and mortality among HFpEF and patients with HFrEF indicated differing mechanistic factors that merit further evaluation.
Perspective:
This is an important study because it shines a light on the interaction between obesity, race, and HF on mortality. As the burden of HF continues to increase, prospective studies are needed to better understand this interaction. Future studies may show clarity if they include the impact of sleep apnea and/or secondary pulmonary hypertension in these obese patients.
Keywords: Body Mass Index, Ethnic Groups, Geriatrics, Heart Failure, Heart Failure, Systolic, Heart Failure, Diastolic, Hospital Mortality, Obesity, Secondary Prevention
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