Panel Series
Abstract
Background: Transcranial photobiomodulation (t-PBM) is a noninvasive modality that may improve cognitive function in both healthy and diseased subjects. Objective: This systematic review and meta-analysis addresses the question of whether t-PBM improves cognitive function in healthy adults. Methods: We searched MEDLINE using PubMed, EMBASE, SCOPUS, Web of Science, and Cochrane Library up to March 2019. We also searched ProQuest and Google Scholar databases for unpublished material. The search was limited to articles on the procognitive effects of t-PBM in healthy adults. The initial search resulted in 871 studies, of which nine publications met our criteria for inclusion and exclusion. Seven studies were performed on young, healthy subjects (17-35 years), and two studies were conducted on older (≥49 years), normal subjects. A meta-analysis was performed on six full-text publications whose subjects were young adults. Results: t-PBM administration improved cognition-related outcomes by an 0.833 standardized mean difference (SMD; 95% confidence interval (CI): 0.458-1.209, 14 comparisons) in young, healthy participants. Funnel plotting revealed asymmetry, which was validated using Egger's (p = 0.030) and Begg's regression (p = 0.006) tests. However after reanalysis, this asymmetry disappeared in the attention subgroup, but not in the memory subgroup. The trim-and-fill analysis indicated two studies were lacking required data. Thus, the effect size was adjusted from an SMD of 0.761 (95% CI: 0.573-0.949) to 0.949 (0.779-1.120). The overall quality score of the studies was modest. Conclusions: We demonstrated a significant, beneficial effect of t-PBM on cognitive performance of young, healthy individuals; however, the heterogeneity of the data was high. This could be due to the modest quality or to the low number of included studies, or to the differences between the various subdomains assessed. These shortcomings should be meticulously addressed before concluding that t-PBM is a cognitive-enhancing intervention in healthy individuals.
Keywords: attention; cognition; healthy adults; learning; memory; transcranial photobiomodulation.
Conflict of interest statement
F.S. is on the Scientific Advisory Board and consultant of Niraxx Light Therapeutics, Inc., and a consultant of ProNeuroLIGHT LLC. Dr. Cassano's salary was supported by the Harvard Psychiatry Department (Dupont-Warren Fellowship and Livingston Award), by the Brain and Behavior Research Foundation (NARSAD Young Investigator Award) and by the Photothera, Inc. unrestricted grant. Drug donation from TEVA. Travel reimbursement from Pharmacia-Upjohn. Dr. Cassano has received consultation fees from Janssen Research and Development. Dr. Cassano has filed a provisional patent related to the use of near-infrared light in psychiatry. PhotoMedex, Inc. supplied four devices for a clinical study. Dr. Cassano is/has 1. Received unrestricted funding from Litecure, Inc. to conduct a study on transcranial photobiomodulation for the treatment of major depressive disorder; 2. Received unrestricted funding from Cerebral Sciences to conduct a study on transcranial photobiomodulation for the treatment of generalized anxiety disorder; 3. Cofounded, member of the board of directors and consultant of Niraxx Light Therapeutics, Inc., a company focused on the development of new modalities of treatment based on near-infrared light. M.R.H. is on the following Scientific Advisory Boards: Transdermal Cap, Inc., Cleveland, OH; BeWell Global, Inc., Wan Chai, Hong Kong; Hologenix, Inc. Santa Monica, CA; LumiThera, Inc., Poulsbo, WA; Vielight, Toronto, Canada; Bright Photomedicine, Sao Paulo, Brazil; Quantum Dynamics LLC, Cambridge, MA; Global Photon, Inc., Bee Cave, TX; Medical Coherence, Boston MA; NeuroThera, Newark DE; JOOVV, Inc., Minneapolis-St. Paul MN; AIRx Medical, Pleasanton CA; FIR Industries, Inc. Ramsey, NJ; UVLRx Therapeutics, Oldsmar, FL; Ultralux UV, Inc., Lansing MI; Illumiheal & Petthera, Shoreline, WA; MB Lasertherapy, Houston, TX; ARRC LED, San Clemente, CA; Varuna Biomedical Corp. Incline Village, NV; Niraxx Light Therapeutics, Inc., Boston, MA; Dr Hamblin has been a consultant for Lexington Int, Boca Raton, FL; USHIO Corp, Japan; Merck KGaA, Darmstadt, Germany; Philips Electronics Nederland B.V.; Johnson & Johnson, Inc., Philadelphia, PA; Sanofi-Aventis Deutschland GmbH, Frankfurt am Main, Germany; Dr Hamblin is a stockholder in Global Photon, Inc., Bee Cave, TX; Mitonix, Newark, DE. The other authors have no conflicts of interest to disclose.
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