Chest Circumference, Stature and Body Mass Index as Determinants of 1918 Influenza Severity

Abstract

Background

Anthropometric traits are established determinants of chronic disease, yet their role in shaping infectious disease outcomes during historical pandemics remains underexplored. During the 2009 H1N1 influenza pandemic, obesity emerged as a novel, independent risk factor for severe illness, raising questions about whether physique and nutritional state have consistently influenced pandemic outcomes across history.

Methods

We present the first large-scale, systematic analysis of body size and influenza severity during the 1918 pandemic, using a newly constructed and validated cohort of World War 1 service men from the Australian Imperial Force (AIF), Canadian Expeditionary Force and New Zealand Expeditionary Force (N = 1444).

Results

Multivariable regression analyses revealed that larger chest circumference was associated with reduced odds of death (odds ratio [OR] 0.90 per 1-cm increase, 95% CI 0.81–0.99). Body mass index (BMI) showed a non-linear association with mortality, with BMI values below 22 kg/m² significantly associated with lower odds of death. Length of hospital stay was shorter among members of the AIF (rate ratio [RR] 0.61, 95% CI 0.54–0.70), and increasing age and height exhibited non-linear associations with longer hospitalisation. BMI was not associated with length of hospitalisation.

Conclusion

Anthropometric measures were associated with influenza outcomes during the 1918 pandemic, although effects were context dependent. These results highlight the continued need to integrate anthropometric and nutritional factors into modern pandemic preparedness frameworks, particularly as populations worldwide continue to face overlapping burdens of undernutrition and obesity.