Cortisol assessment and classification
During the original trial, blood was systematically collected upon inclusion to the study and stored for further batch analyses. Samples were taken in the morning (i.e. 6–7 am) within 48 h of admission. We stratified admission cortisol levels into quartiles and defined two categories: patients with levels in the highest quartile (> 723 nmol/l) were defined as “high cortisol” while patients in the lower 3 quartiles (≤ 723 nmol/l) were assigned the “low cortisol” group.