307 - Limits of the Obesity Paradox: Obese Patients with Heart Failure are at Higher Risk of Hospitalization

Abstract

Introduction: “Obesity Paradox” describes the consistent finding that obese patients with HF have a lower mortality rate than patients with HF at normal body-mass indices (BMI). Obesity's impact on HF and non-HF hospitalization risks following HF hospitalization is unknown. We hypothesize increasing obesity will increase the rate of 30-day all cause hospital readmissions following an index HF hospitalization compared to a normal BMI. Methods: We analyzed all patients (n = 1,454) age ≥ 65 years with Centers of Medicare Services (CMS) benefits and a primary discharge diagnosis of HF from an academic medical center who were included in the CMS Hospital Readmission Reduction Program report from 2009 - 2014. Obesity was classified by BMI according to the World Health Organization: Underweight (BMI <18.5 kg/m2), Normal (18.5–24.9 kg/m2), Overweight (25.0–29.9 kg/m2), Class I Obesity (30.0–34.9 kg/m2), Class II Obesity (35.0–39.9 kg/m2), and Morbid Obesity (≥40.0 kg/m2). The primary outcome was 30-day all-cause readmission to any hospital after a HF admission. Mortality was assessed using the CMS Inpatient Quality Report on HF 30-day mortality. Readmission reasons were classified by primary discharge diagnosis using Clinical Classification Software from the AHRQ. Results: The cohort BMI distribution consisted of 2.9% Underweight, 29.1% Normal, 30.3% Overweight, 19.7% Class I Obesity, 9.5% Class II Obesity, and 8.5% Morbid Obesity. Compared to Normal BMIs, those in elevated BMI groups were younger (P < .001) and had a higher prevalence of diabetes (P < .0001) and obstructive sleep apnea (P < .0001). The cohort's 30-day all cause readmission rate was 21.3 % (n = 309) and 30-day mortality rate was 7.1% (n = 103). Compared to the 30-day all cause readmission rate in the Normal BMI group (16.8%), readmissions were more frequent among the Overweight (22.4%; P = .04), Class I Obesity (26.8%, P = .001), Class II Obesity (24.6%, P = .04), but not Morbid Obesity (18.7%, P = .6). Mortality rates were lower among the Overweight (6.1%; P = .04), Class I Obesity (5.2%, P = .02), Class II Obesity (3.6%, P = .02), but not Morbid Obesity (6.5%, P = .2) compared to the Normal BMI group (9.9%). Of the 309 readmissions, the most frequent reasons were HF (n = 107; 35%), infection (n = 32; 10%), and AKI (n = 25; 9%). The percentage of readmissions from non-HF diagnoses were similar across BMI groups: Normal (66%), Overweight (63%), Class I Obesity (62%), Class II Obesity (68%), except Morbid Obesity (83%). Conclusions: In contrast to paradoxical effects on mortality, elevated BMI increased the rate of hospitalization after a HF admission compared to a normal BMI, except in the morbidly obese.