Authors: MP Tulppo¹, AM Kiviniemi¹, AJ Hautala¹, J Karjalainen¹, JJ Jaakkola², TM Ikaheimo², J Nissila³, H Jurvelin³, T Takala⁴, HV Huikuri^5
1Verve Research, Department of Exercise and Medical Physiologic – Oulu – Finland
²Centre for Environmental and Respiratory Health Research, University of Oulu – Oulu – Finland
³Department of Biology, University of Oulu – Oulu – Finland
⁴Oulu Deaconess Institute – Oulu – Finland
⁵Institute of Clinical Medicine, University of Oulu – Oulu – Finland

Purpose: A recent study suggests that transcranial brain targeted light treatment via ear canals may have physiological effects on brain function studied by functional magnetic resonance imaging techniques in humans. We tested the hypothesis that an acute transcranial bright light treatment via ear canals may have effects on autonomic regulation in mild hypertensive subjects.
Methods: Hypertensive men without any medication participated in the study (n=19, age 61±3 years, systolic blood pressure 140-160 and/or diastolic blood pressure 90-100 mmHg during one week follow up at home). In a blinded study design, a twelve min dose of bright light treatment or sham treatment were administered in a random order on separate days by a transcranial bright light device via the ear canals (blue based LEDs). Blood pressure and ECG were measured during the treatments. Heart rate variability was analyzed in 5 min periods at baseline, at the end of treatment, immediately following and from 7 to 12 min after treatment. Standard deviation of R-R intervals (SDNN) and high (HF), low (LF) and very low (VLF) frequency powers of R-R intervals were calculated by standard spectral techniques. Analysis of variance for repeated measures with time x group interaction was performed for the measured variables.
Results: There was no time x group interaction in heart rate or blood pressure. SDNN and VLF power increased during the bright light treatment but not during the sham treatment (time x group interaction p=0.019 and p=0.040 for SDNN and VLF, respectively). VLF power was 6.7±0.7 vs. 6.6±0.6 ln ms2 (p=ns) at baseline for bright light treatment and sham, respectively. The corresponding VLF values for bright light and sham were 7.0±0.7 vs. 6.6±0.7 (p=0.034) at the end of treatment, 7.3±0.7 vs. 6.8±0.7 (p=0.013) immediately after treatment and 6.9±0.5 vs. 6.9±0.6 ln ms2 (p=ns) at the end of the recordings. LF or HF power did not differ between treatments (interaction p=0.33 for both).
Conclusion: The results of this blinded and sham controlled trial provide evidence that acute transcranial bright light treatment via ear canals have effects on cardiovascular autonomic regulation in hypertensive males documented by increasing long-term heart rate variability indices.