Transcranial Photobiomodulation (tPBM) With 1,064-nm Laser to Improve Cerebral Metabolism of the Human Brain In Vivo

Background and Objectives In our previous proof-of-principle study, transcranial photobiomodulation (tPBM) with 1,064-nm laser was reported to significantly increase concentration changes of oxygenated hemoglobin ( increment [HbO]) and oxidized-state cytochromecoxidase ( increment [oxi-CCO]) in the human brain. This paper further investigated (i) its validity in two different subsets of young human subjects at two study sites over a period of 3 years and (ii) age-related effects of tPBM by comparing sham-controlled increases of increment [HbO] and increment [oxi-CCO] between young and older adults. Study Design/Materials and Methods We measured sham-controlled increment [HbO] and increment [oxi-CCO] using broadband near-infrared spectroscopy (bb-NIRS) in 15 young (26.7 +/- 2.7 years of age) and 5 older (68.2 +/- 4.8 years of age) healthy normal subjects before, during, and after right-forehead tPBM/sham stimulation with 1,064-nm laser. Studentttests were used to test statistical differences in tPBM-induced increment [HbO] and increment [oxi-CCO] (i) between the 15 young subjects and those of 11 reported previously and (ii) between the two age groups measured in this study. Results Statistical analysis showed that no significant difference existed in increment [HbO] and increment [oxi-CCO] during and post tPBM between the two subsets of young subjects at two study sites over a period of 3 years. Furthermore, the two age groups showed statistically identical net increases in sham-controlled increment [HbO] and increment [oxi-CCO]. Conclusions This study provided strong evidence to validate/confirm our previous findings that tPBM with 1,064-nm laser enables to increase cerebral increment [HbO] and increment [oxi-CCO] in the human brain, as measured by bb-NIRS. Overall, it demonstrated the robust reproducibility of tPBM being able to improve cerebral hemodynamics and metabolism of the human brainin vivoin both young and older adults. Lasers Surg. Med. (c) 2020 The Authors.Lasers in Surgery and Medicinepublished by Wiley Periodicals, Inc.