Body mass index and survival in people with heart failure.

Aims: In people with heart failure (HF), a high body mass index (BMI) has been linked with better outcomes ('obesity paradox'), but there is limited evidence in community populations across long-term follow-up. We aimed to examine the association between BMI and long-term survival in patients with HF in a large primary care cohort.

Methods: We included patients with incident HF aged ≥45 years from the Clinical Practice Research Datalink (2000-2017). We used Kaplan-Meier curves, Cox regression and penalised spline methods to assess the association of pre-diagnostic BMI, based on WHO classification, with all-cause mortality.

Results: There were 47 531 participants with HF (median age 78.0 years (IQR 70-84), 45.8% female, 79.0% white ethnicity, median BMI 27.1 (IQR 23.9-31.0)) and 25 013 (52.6%) died during follow-up. Compared with healthy weight, people with overweight (HR 0.78, 95% CI 0.75 to 0.81, risk difference (RD) -4.1%), obesity class I (HR 0.76, 95% CI 0.73 to 0.80, RD -4.5%) and class II (HR 0.76, 95% CI 0.71 to 0.81, RD -4.5%) were at decreased risk of death, whereas people with underweight were at increased risk (HR 1.59, 95% CI 1.45 to 1.75, RD 11.2%). In those underweight, this risk was greater among men than women (p value for interaction=0.02). Class III obesity was associated with increased risk of all-cause mortality compared with overweight (HR 1.23, 95% CI 1.17 to 1.29).

Conclusion: The U-shaped relationship between BMI and long-term all-cause mortality suggests a personalised approach to identifying optimal weight may be needed for patients with HF in primary care. Underweight people have the poorest prognosis and should be recognised as high-risk.