Obesity Definitions and Hospital Stay in Older Adults with Heart Failure: A Post Hoc Analysis of a Prospective Cohort

Background: The prognostic significance of obesity in patients hospitalised for acute heart failure (HF) remains uncertain, particularly among older adults. This study aimed to assess whether three obesity definitions – BMI, waist circumference and the clinical obesity framework – predict hospital length of stay (LOS) in older adults hospitalised for acute decompensated HF. Methods: This post hoc exploratory analysis used data from a prospective cohort of 250 adults aged ≥60 years hospitalised for acute decompensated HF. Obesity was defined as: BMI ≥30 kg/m²; waist circumference ≥102 cm in men or ≥88 cm in women; and clinical obesity per the Lancet Diabetes & Endocrinology Commission, applied post hoc. LOS was modelled using univariable and multivariable negative binomial regression. Results: None of the three obesity definitions were independently associated with LOS. In the multivariable models, only N-terminal pro-B-type natriuretic peptide (NT-proBNP) was an independent predictor of LOS in patients with clinical obesity (incidence rate ratio [IRR] 1.004 per 100 pg/ml; p=0.004). Among those with classical obesity, New York Heart Association class IV (IRR 2.355; p=0.004), NT-proBNP (IRR 1.004; p=0.004), and smoking history of 41–50 pack-years (IRR 1.946; p=0.022) remained independently associated with longer LOS. For central obesity, haemoglobin (IRR 0.923; p=0.029) and NT-proBNP (IRR 1.004; p<0.001) were significant predictors. Conclusion: In this cohort of older adults hospitalised for acute decompensated HF, none of the three obesity definitions – including the new clinical obesity framework – were independent predictors of LOS.