The Circadian Temperature Trajectory Predicts the Severity and Prognosis in Critically Ill Patients

Abstract Background: Disrupted circadian temperature is commonly observed in patients in the intensive care unit (ICU). The aim of this study is to examine the association between body temperature (BT) circadian rhythm and mortality critically in patients receiving ICU admission for at least 24h.Method: Adult patients with a complete record of temperature during the first 24 hours of ICU stay in the Multi-parameter Intelligent Monitoring in Intensive Care III (MIMIC-III) database were included in this retrospective cohort study. Body temperature circadian rhythm ratio (BTCRR) was calculated according to the value of mean nighttime divided by daytime mean temperature. All patients were divided into the nocturnal BT rising (NBTR) group (BTCRR >1) and the non-NBTR group (BTCRR≤1). Five subgroups were also built according to different quantile of BTCRR (5%, 10%, 30%, 50%). The associations of NBTR, subgroup, and BTCRR with 28-day mortality were assessed separately using Cox proportional hazards model.Findings: The overall cohort comprised 32419 patients. The non-NBTR group (n=20148) had higher 28-day mortality than the NBTR group (n=12271). After adjusting for covariates, the analysis showed that NBTR was significantly associated with mortality at 28 days (hazard ratio: 0.923; 95% CI, 0.888–0.960, P<0.05). All results of subgroup analysis showed obvious statistical significance, and similar results persisted in the patients with different groups. The % BTCRR had a significant non-linear (p < 0.05) association with 28d-mortality after adjusting for other variables (p < 0.05). Increasing the percentage up to 101% resulted in a hazard ratio (HR) to reduced mortality (HR: 0.96; 95%, 0.941–0.972, P<0.001), while increases above 101 % didn’t make a significant suggestion in mortality.Conclusions: The findings of this study suggest that both low and high BTCRR indicates a poor outcome, such that having a BTCRR of 101% had a survival advantage. BTCRR may aid in the early identification of critically ill patients at high risk of 28-day mortality. These findings may provide a basis for future randomized controlled trials comparing temperature control of ICU patients.