Related Experiment Video
Updated: Feb 14, 2026

Cell Dissociation from the Tongue Epithelium and Mesenchyme/Connective Tissue of Embryonic-Day 12.5 and 8-Week-Old Mice
Published on: January 21, 2021
Associations of postoperative mortality with the time of day, week and year
1Department of Anaesthesiology, Medical Faculty, RWTH Aachen University, Aachen, Germany.
Abstract:
Studies that have investigated circadian, weekday and seasonal variation in postoperative mortality have been relatively small or have been for scheduled surgery. We retrospectively tested a large mixed surgical cohort from a German tertiary care university hospital for the presence of cyclical variation in all-cause in-hospital mortality after operations performed between 2006 and 2013. We analysed mortality rates after 247,475 operations, adjusted for age, sex, comorbidities, location, urgency and duration of the surgery, and intra-operative blood transfusions. The mortality odds ratio (95%CI) after operations started in the morning (08:00-11:00) were lowest, 0.73 (0.66-0.80), p < 0.001 and highest for operations started in the afternoon (13:00-17:00), 1.29 (1.18-1.40), p < 0.001. Mortality at the weekend was the same as during the week. There was no seasonal variation in mortality, p = 0.12. However, the interference of four-yearly and ten-monthly cycle amplitudes resulted in higher mortality odds ratio (95%CI) in winter 2008-2009, 1.41 (1.18-1.69), p < 0.001, and lower mortality in spring 2011 and 2012, 0.70 (0.56-0.85) and 0.67 (0.53-0.85), p < 0.001 and p = 0.001, respectively. The ability to predict cyclical phenomena would facilitate the design of interventional studies, aimed at reducing mortality following surgery in the afternoon and when cycles interfere constructively.
Related Concept Videos
Associative Learning
Classical conditioning, also known...
Association Areas of the Cortex
Prefrontal Association Area: This area is located in the frontal lobe and is involved in planning, decision-making, and moderating social behavior. It connects with primary motor areas,...
Peripheral Artery Disease V: Postoperative Nursing Management
Genome-wide Association Studies-GWAS
GWAS does not require the identification of the target gene involved in...
Somatosensory, Motor, and Association Cortex
Mixing Time

