The impact of body mass index on long-term survival after ICU admission due to COVID-19: A retrospective multicentre study

Ashwin Subramaniam; Ryan Ruiyang Ling; Emma J Ridley; David V Pilcher

doi:10.1016/j.ccrj.2023.10.004

The impact of body mass index on long-term survival after ICU admission due to COVID-19: A retrospective multicentre study

Crit Care Resusc. 2023 Nov 22;25(4):182-192. doi: 10.1016/j.ccrj.2023.10.004. eCollection 2023 Dec.

Authors

Ashwin Subramaniam^{1

2

3

4}, Ryan Ruiyang Ling⁵, Emma J Ridley^{4

6}, David V Pilcher^{4

7

8}

Affiliations

¹ Department of Intensive Care, Peninsula Health, Frankston, Victoria, Australia.
² Department of Intensive Care, Dandenong Hospital, Monash Health, Dandenong, Victoria, Australia.
³ Peninsula Clinical School, Monash University, Frankston, Victoria, Australia.
⁴ Australian and New Zealand Intensive Care Research Centre (ANZIC-RC), School of Public Health and Preventive Medicine, Monash University, Melbourne, Victoria, Australia.
⁵ Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
⁶ Department of Nutrition and Dietetics, Alfred Hospital, Melbourne, Victoria, Australia.
⁷ Department of Intensive Care, Alfred Hospital, Melbourne, Victoria, Australia.
⁸ Centre for Outcome and Resource Evaluation, Australian and New Zealand Intensive Care Society, Melbourne, Victoria, Australia.

Abstract

Objective: The impact of obesity on long-term survival after intensive care unit (ICU) admission with severe coronavirus disease 2019 (COVID-19) is unclear. We aimed to quantify the impact of obesity on time to death up to two years in patients admitted to Australian and New Zealand ICUs.

Design: Retrospective multicentre study.

Setting: 92 ICUs between 1st January 2020 through to 31st December 2020 in New Zealand and 31st March 2022 in Australia with COVID-19, reported in the Australian and New Zealand Intensive Care Society adult patient database.

Participants: All patients with documented height and weight to estimate the body mass index (BMI) were included. Obesity was classified patients according to the World Health Organization recommendations.

Interventions and main outcome measures: The primary outcome was survival time up to two years after ICU admission. The effect of obesity on time to death was assessed using a Cox proportional hazards model. Confounders were acute illness severity, sex, frailty, hospital type and jurisdiction for all patients.

Results: We examined 2,931 patients; the median BMI was 30.2 (IQR 25.6-36.0) kg/m². Patients with a BMI ≥30 kg/m² were younger (median [IQR] age 57.7 [46.2-69.0] vs. 63.0 [50.0-73.6]; p < 0.001) than those with a BMI <30 kg/m². Most patients (76.6%; 2,244/2,931) were discharged alive after ICU admission. The mortality at two years was highest for BMI categories <18.5 kg/m² (35.4%) and 18.5-24.9 kg/m² (31.1%), while lowest for BMI ≥40 kg/m² (14.5%). After adjusting for confounders and with BMI 18.5-24.9 kg/m² category as a reference, only the BMI ≥40 kg/m² category patients had improved survival up to 2 years (hazard ratio = 0.51; 95%CI: 0.34-0.76).

Conclusions: The obesity paradox appears to exist beyond hospital discharge in critically ill patients with COVID-19 admitted in Australian and New Zealand ICUs. A BMI ≥40 kg/m² was associated with a higher survival time of up to two years.

Keywords: ANZICS adult patient database; Body mass index; COVID-19; Long-term survival; Obesity; Obesity paradox.