Association Between Sleep Quality and Oxidative Stress in Postoperative Cardiovascular Patients-A Pilot Study

Oxidative stress contributes to numerous physiological and pathological processes, and sleep behaviour as well as circadian rhythms may influence reactive oxygen species (ROS) concentrations in humans. This prospective pilot study quantified postoperative venous ROS concentrations in patients undergoing cardiovascular surgery and explored associations with subjective and objective sleep parameters, circadian patterns and patient characteristics. Fifteen patients undergoing cardiovascular surgery at the University Medical Center Freiburg were monitored during the first 48 postoperative hours. Serial venous blood samples were analysed for ROS concentrations using electron spin resonance. Sleep was assessed using validated questionnaires, including the Insomnia Severity Index, Pittsburgh Sleep Quality Index and Schlaffragebogen-A (SF-A), as well as actigraphy. Additional clinical data were recorded. Venous ROS concentrations showed substantial inter-individual variability but no significant circadian pattern. Mean postoperative ROS concentrations were not significantly associated with ISI scores, PSQI global score, SF-A parameters or objective actigraphic sleep measures. Among PSQI subdomains, however, higher ROS concentrations were significantly associated with reduced sleep efficiency (r = -0.74, p = 0.002) and longer nocturnal wake time (r = 0.62, p = 0.01), while shorter sleep duration showed a trend-level association (r = -0.49, p = 0.07). These findings demonstrate the feasibility of electron spin resonance-based venous ROS quantification in postoperative cardiac surgery patients. Specific subjective sleep parameters, particularly reduced sleep efficiency and increased nocturnal wake time, may be associated with higher postoperative ROS concentrations. Larger studies are warranted to confirm these exploratory findings.