From previous analyses of this high-quality clinical database, levels of missing data are anticipated to be very low. Patients missing the primary outcome or key confounders (age, location prior to admission, primary reason for admission) will therefore be excluded from the analysis. Patients missing other binary/categorical confounders/mediators will be assumed to be in the lowest risk category (i.e. no severe conditions in past medical history, no assistance with daily activities, no CPR, no delay). Following standard approaches, missing physiological parameters will be assumed to be normal and assigned zero points in the ICNARC Physiology Score (except for patients missing all physiology, who will be excluded).