Background: Dysregulation of the circadian rhythm is linked to immune response deficiencies. Diurnal temperature variation-a surrogate for the circadian rhythm, exists in humans, yet its preservation during illness is not well understood.
Materials and methods: Temperatures measured within one-half hour of 8 am, 12 pm, 4 pm, 8 pm, 12 am, and 4 am from 16,245 hospitalized patients were statistically analyzed.
Results: Although we found a diurnal pattern when analyzing the ensemble of temperatures from all patients, stratified by measurement site, the trough-to-peak difference was only 0.2°F, while that for healthy volunteers had been in the 0.5°F to 1.9°F range. The peaks occurred at 8 pm for all patients, regardless of age or sex, which is similar to healthy people. However, the troughs were shifted to later times compared with the 6 am in healthy people-for young patients (age 20-30 years) the trough was at 8 am and for elderly patients (age 70-80 years), at 12 pm, again regardless of patients' sex. Analysis of individual patients showed that less than 20% of patients exhibited diurnal variation and among those showing variation, the trend was present only on the minority of hospitalization days. The presence or absence of an infectious process or fever did not influence the proportion of patients showing diurnal variation.
Conclusions: Hospitalization is associated with disruption in the circadian rhythm as reflected by patients' body temperature. Since abnormality in body temperature is known to affect patient outcomes, an understanding of the diurnal cycle during hospitalization is the first step towards devising approaches to re-establish the circadian rhythm.
Keywords: Body temperature; Circadian rhythm; Diurnal variation; Fever; Hypothermia.
Copyright © 2021. Published by Elsevier Inc.