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The Effect of Colored Illumination on Heart Rate Variability

We investigated the effects of illumination with colored fluorescent light on heart rate variability (HRV) and autonomic regulation. Previous examinations have only focused on full-spectrum fluorescent bright light as it is used for the therapy of seasonal affective disorder and disturbances of circadian rhythms. Materials and Methods: In 3 experiments, 12 healthy volunteers were exposed for 10 min to red, green and blue fluorescent light of 700 lux, respectively. These illumination periods were followed and preceded by 15 min of darkness. HRV series were recorded within the last minutes of each illumination and darkness period. HRV analysis encompassed time domain variables, frequency domain variables and detrended fluctuation analysis (DFA). Results: DFA yielded a highly significant increase of the self-similarity parameter aDFA under red and green illumination, while blue light was accompanied by a decrease. A spectral analysis revealed parallel behavior of very low frequency components in the range of 0.003-0.04 Hz. Green light also seemed to induce a reduction in high frequency components. Conclusions: Results show that colored light can influence HRV within minutes and that the effects of individual colors can be distinguished by HRV analysis.