Investigating the Effect of Different Wavelength of Light on Heart Rate Variability and Perfusion Index

Light influences on our physical, mental and emotional health. It can suppress or stimulate physiological responses in human beings, the extent of which depends on the wavelength, duration and intensity of light exposure. The study was designed to investigate the impact of different colored illumination, using non-invasive means on the heart rate variability and perfusion index. Electrocardiogram (ECG) and pulse oximetry are non-invasive recording of the cardiac activity. Thus, this paper reports experimental research conducted where changes in heart rate (HR), Heart rate variability (HRV)through ECG and perfusion index (PI) via pulse oximetry were measured when the participants were exposed to different wavelength of light (Blue, Red, and Green). The results of these experiments show that there is a change in heart rate, variability and perfusion index when a subject is exposed to different wavelengths. There was a decrease in HR and PI after the exposure, significantly for blue $( \mathrm{p} < 0.0001, \mathrm{p} < 0.0002)$ and green $( \mathrm{p} < 0.0098, \mathrm{p} < 0.0150)$ (shorter wavelength) color, while significant increase in HRV (blue $( \mathrm{p} < 0.0001)$, green $( \mathrm{p} < 0.0451)$). The case was opposite for red color.