Chronobiology of the Autonomic Nervous System

*Chronobiology - The Science of Biological Time Structure*

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**Chapter 5**

**Abstract**

Circadian Rhythms of the

Scientific Implication and

Practical Implementation

*and Elisabeth M. Balint*

application in medical consultation.

**1. Introduction**

Autonomic Nervous System:

*Marc N. Jarczok, Harald Guendel, Jennifer J. McGrath* 

Circadian rhythms are omnipresent in almost any biosignal. In this chapter, we join them with the need for practical tools for screening in preventive settings and point out heart rate variability (HRV), a measure of autonomic nervous system activity, as a chronobiologic, unspecific index of mental and physical health. We discuss methods to calculate the circadian variation of HRV measures, particularly the cosinor procedure. We present reference values for circadian variation parameters of HRV and data concerning reproducibility. Furthermore, we show data giving first evidence of HRV as a comprehensive health index by showing altered circadian variation patterns of HRV depending on mental (trait dysthymia) as well as physical (inflammatory markers) health. Finally, we present examples of disturbed chronobiology of HRV in clinical and preventive settings and its practical

**Keywords:** circadian variation, heart rate variability, prevention, health index,

Circadian rhythms are omnipresent in nearly all biosignals particularly including heart rate (HR) and blood pressure [1]. Technological advances in wearables and ambulatory monitoring have made the continuous recording of real-time data highly accessible for health researchers and clinicians. Consider, 24–48 h recordings of blood pressure are frequently used in the clinical context to determine what grade of hypertension a patient has to ensure better options for treatment [2, 3]. In other areas, systematic and statistical analysis of circadian rhythms may offer adjuvant avenues such as in occupational medicine. Nonetheless, traditional approaches in this field included foremost prevention of injuries, e.g., from chemical or other environmental hazards. In the past years, the catalog of potential hazards was extended to mental health-related problems like stress and communicative problems. Moreover, the tasks in occupational medicine include now an active (occupational) health management

vagal activity, occupational medicine, autonomic nervous system

**1.1 The need for practical tools for screening in preventive settings**
