Work

Differential impact of sex and age on the obesity paradox: A retrospective observational study of a binational registry

Year: 2025

Type: article

Abstract: Background An increased body mass index (BMI) is associated with improved outcomes in intensive care unit patients, known as the "obesity paradox". Objective The objective of this study was to investigate whether sex and age modify the obesity paradox. Methods We performed a retrospective, multicentre, observational study of a binational registry. All patients with a recorded BMI admitted to the intensive care unit in Australia and New Zealand between 2010 and 2022 were included in the study cohort. The primary outcome was in-hospital mortality. Using multivariable models, we analysed the impact of sex and age on the relationship between BMI and outcome. Results We studied 957 873 patients (565 759 men and 392 114 women; median BMI: 27.8 kg/m 2 for both groups). For both groups, an increased BMI was associated improved survival, for a BMI up to >35 kg/m 2 . However, this protective association was modified by sex. At a BMI of 30 kg/m 2 , compared to a baseline BMI of 22.5 kg/m 2 , an odds ratio (OR) (95% confidence interval [CI]) of 0.83 (0.81–0.87) was estimated for men and 0.93 (0.89–0.98) for women, implying a stronger association for men. Furthermore, the paradox was also modified by age with a more pronounced effect for older patients. For men, the OR of 0.89 (0.82–0.98) at a BMI of 30 kg/m 2 and age of 40 years reduces to 0.80 (0.76–0.84) at the same BMI and an age of 75 years. For women, the OR of 0.99 (0.92–1.13) at a BMI of 30 kg/m 2 and age of 40 years reduces to 0.89 (0.84–0.93) at the same BMI and an age of 75 years. Conclusion The obesity paradox is modified by both sex and age. The paradox is more pronounced for men and within the group of older patients.

Source: Australian Critical Care

DOI: 10.1016/j.aucc.2025.101461

Authors: Drago Plečko, Lucy Modra, David Pilcher, Rinaldo Bellomo