Body mass index and survival in people with heart failure
Authors: Jones N , Ordonez-Mena J M , Roalfe A K , Goyder C , Hobbs F D R , Taylor C J 
Published: October 2022

Abstract

Background
People with obesity are twice as likely to develop heart failure (HF) compared to people with a healthy body mass index (BMI) [1]. However, among people with HF a higher BMI has been linked to a reduced risk of all-cause mortality, a concept known as the “obesity paradox” [2].

Purpose
To examine the association between BMI and survival in patients with chronic HF among a large primary care cohort.

Methods
We extracted data from the Clinical Practice Research Datalink of primary care records from 1st January 2000 to 31st December 2017 and included 47,531 patients with an incident diagnosis of HF, who were aged 45 years and over and who had a recorded BMI. Patients were stratified into categories of baseline BMI as underweight (BMI &lt;18.5 kg/m2), healthy weight (BMI 18.5 to 24.9 kg/m2), overweight (BMI 25.0 to 29.9 kg/m2) or obese, with obesity split into class I (30.0–34.9 kg/m2), class II (35.0–39.9 kg/m2) and class III (40 kg/m2 and over). The primary outcome was all-cause mortality. We used Kaplan-Meier curves and log rank tests to compare survival in people with HF, based on baseline BMI. We also report a Cox regression model for risk of all-cause mortality among people with HF comparing BMI categories.

Results
There were 25,013 deaths during the study follow-up. The average age of participants was 77.1 years (SD 10.6) and mean BMI was 27.9 (SD 6.1). In an age- and sex-adjusted analysis, people who were underweight were at increased risk of all-cause mortality compared to people with healthy weight (HR 1.52, 95% CI 1.41 to 1.64). People with overweight (HR 0.81, 95% CI 0.79 to 0.84), obesity class I (HR 0.79, 95% CI 0.76 to 0.82) and obesity class II (HR 0.78, 95% CI 0.74 to 0.82) were at decreased risk of all-cause mortality. People with obesity class III had no difference in risk of death compared to people with healthy weight (HR 0.95, 95% CI 0.88 to 1.02). In a Kaplan-Meier analysis, there was an inverse relationship between body weight and risk of death, even within the first year of follow-up.

Conclusion
In our large community cohort of people with HF, we found an inverse relationship between BMI and survival. Underweight people with HF have the poorest prognosis and should be identified as high-risk. Conversely, people with HF who are overweight or obese (class I and II) are at lower risk of death confirming the obesity paradox in a real-world primary care population. These findings suggest a more cautious approach to weight management in overweight and obese patients may be needed for people with HF in primary care.

Funding Acknowledgement
Type of funding sources: Public grant(s) – National budget only. Main funding source(s): The SurviveHF study was funded by the National Institute for Health Research (NIHR) Collaboration for Leadership in Applied Health Research and Care (CLAHRC) Oxford at Oxford Health NHS Foundation Trust and the Wellcome Institutional Strategic Fund. The funders did not have any role in the design of the study, analysis and interpretation of the data, or writing of the results for publication.