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BACKGROUND: Disrupted vital-sign circadian rhythms in the intensive care unit (ICU) are associated with complications such as immune system disruption, delirium and increased patient mortality. However, the prevalence and extent of this disruption is not well understood. Tools for its detection are currently limited. METHODS: This paper evaluated and compared vital-sign circadian rhythms in systolic blood pressure, heart rate, respiratory rate and temperature. Comparisons were made between the cohort of patients who recovered from the ICU and those who did not, across three large, publicly available clinical databases. This comparison included a qualitative assessment of rhythm profiles, as well as quantitative metrics such as peak-nadir excursions and correlation to a demographically matched 'recovered' profile. RESULTS: Circadian rhythms were present at the cohort level in all vital signs throughout an ICU stay. Peak-nadir excursions and correlation to a 'recovered' profile were typically greater throughout an ICU stay in the cohort of patients who recovered, compared to the cohort of patients who did not. CONCLUSIONS: These results suggest that vital-sign circadian rhythms are typically present at the cohort level throughout an ICU stay and that quantitative assessment of these rhythms may provide information of prognostic use in the ICU.

Original publication




Journal article


Crit Care

Publication Date





Blood pressure, Circadian rhythms, Delirium, Intensive care, Intensive care unit, Vital sign monitoring, Adult, Aged, Blood Pressure, Circadian Rhythm, Female, Heart Rate, Humans, Intensive Care Units, Male, Middle Aged, Vital Signs