Sebastian  Kohl,Mariangela  Schmitt,Ulrike  Bauer,Markus  Canazei,Wilfried  Pohl,Otmar  Pachinger,Markus Stuehlinger,
Effects of Red and Blue Light on the Cardiac Autonomic Nervous System
Journal of Integrative Cardiology Open Access
2020
2674-2489
http://dx.doi.org/10.31487/j.JICOA.2020.04.06
https://www.sciencerepository.org/effects-of-red-and-blue-light-on-the-cardiac-autonomic_JICOA-2020-4-106 
Abstract: Purpose: Light is an important environmental stimulus influencing everyday life. However, information
about the impact of coloured light on the autonomic nervous system (ANS) is sparse. In general, red light
(RL) is thought to act as an adrenergic trigger, while there is evidence that blue light (BL) induces
parasympathetic activation. This is a pilot study to find out, if RL and/or BL affects heart rate variability
(HRV).
Methods: Participants were randomly exposed first to neutral light (NL) and then to RL and BL for 120
minutes in a special light cabin. During each test run, HRV measurements were performed using both wrist
training computers and Holter-ECGs. Furthermore, heart rate, arrhythmias and blood pressure were
analysed. All parameters were measured during neutral and repeated during RL or BL in 10 supraventricular
tachycardia patients, in 10 patients with heart failure and 10 athletes.
Results: During exposure to both RL and BL an increase of blood pressure, improvements of several HRV
parameters, but no significant change of heart rate was observed. Neither RL nor BL influenced the
occurrence of ectopic beats in Holter ECGs. The most prominent improvement of HRV was found in
athletes, whereas increase in blood pressure were comparable between all three groups.
Conclusion: RL and BL influence the cardiac ANS. Since no differences were found between different
light scenarios, the changes can not solely be attributed to the two-sided model of sympathetic and
parasympathetic effects of ANS. However, RL and BL could potentially be used therapeutically to influence
HRV in athletes.Keywords: parasympathetic, cholinergic, adrenergic, heart rate variability, light therapy, blood pressure