Photobiomodulation and visual stimulation against cognitive decline and Alzheimer’s disease pathology: a systematic review

• Published in: Alzheimer's & dementia : translational research & clinical interventions Vol. 8; no. 1; pp. 1 - 24
• Main Authors: Monteiro, Francisca Machado, Carvalho, Óscar Samuel Novais, Sousa, Nuno, Silva, Filipe Samuel, Sotiropoulos, I.
• Format: Journal Article
• Language: English
• Published: United States Wiley 2022; John Wiley & Sons, Inc; John Wiley and Sons Inc
• Subjects: Alzheimer's disease; Animal cognition; Apoptosis; Cell growth; Cognitive ability; Cognitive decline; Dementia; Light therapy; light‐based therapies; Morphology; Neurodegeneration; Neuropathology; Pathology; Photobiomodulation; Proteins; Review; Science & Technology; Systematic review; Visual stimulation; light‐based therapies; photobiomodulation; cognitive decline; Alzheimer's disease; visual stimulation
• ISSN: 2352-8737; 2352-8737
• DOI: 10.1002/trc2.12249

Introduction: Given the ineffectiveness of the available drug treatment against Alzheimer disease (AD), light-based therapeutic modalities have been increasingly receiving attention with photobiomodulation (PBM) and, more recently, visual stimulation (VS) being among the most promising approaches. However, the PBM and VS light parameters tested so far, as well as their outcomes, vary a lot with conflicting results being reported. Methods: Based on Scopus, PubMed, and Web of Science databases search, this systematic review summarizes, compares, and discusses 43 cell, animal, and human studies of PBM and VS related to cognitive decline and AD pathology. Results: Preclinical work suggests that PBM with 640±30-nm light and VS at 40 Hz attenuates Aβ and Tau pathology and improves neuronal and synaptic plasticity with most studies pointing towards enhancement of degradation/clearance mechanisms in the brain of AD animal models. Despite the gap of the translational evidence for both modalities, the few human studies performed so far support the use of PBM at 810- 870 nm light pulsing at 40 Hz for improving brain network connectivity and memory in older subjects and AD patients, while 40 Hz VS in humans seems to improve cognition; further clinical investigation is urgently required to clarify the beneficial impact of PBM and VS in AD patients. Discussion: This review highlights PBM and VS as promising light-based therapeutic approaches against AD brain neuropathology and related cognitive decline, clarifying the most effective light parameters for further preclinical and clinical testing and use. This systematic review was supported by FCT (Fundação para a Ciência e Tecnologia) through the grant with reference SFRH/BD/09375/2020 and by FCT national funds, under the national support to R&D units grant, through the reference project UIDB/04436/2020 and UIDP/04436/2020. This is also supported by the project PTDC/EME-EME/1681/2021 - BrainStimMap and the project NORTE-01-0145-FEDER-000023, supported by the Northern Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (FEDER). This work has been also funded by National funds, through the Foundation for Science and Technology (FCT)-project UIDB/50026/2020 and UIDP/50026/2020 and by the projects NORTE-01-0145-FEDER-000013 and NORTE- 01-0145-FEDER-000023, the Project Estratégico co-funded by FCT (PEst-C/SAU/LA0026/2013) and the European Regional Development Fund COMPETE (FCOMP-01-0124-FEDER-037298; POCI-01-0145- FEDER-007038) supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF).