Improved cognitive function, efficiency, saccadic eye movement, and depressive symptoms in mild cognitive impairment with transcranial photobiomodulation

Background: Mild cognitive impairment (MCI) is a critical stage with higher progression to Alzheimer's disease, yet effective interventions are still lacking. Objective: Some empirical studies have shown that transcranial photobiomodulation (tPBM) may be effective in enhancing cognitive function. To further investigate its effectiveness, a controlled experiment was conducted. Methods: In this study, 36 community-dwelling older adults with MCI were assigned to receive either real tPBM (experimental group; n = 25) and others without intervention (control group; n = 11) over three weeks. Participants underwent comprehensive assessments before and after the intervention, including neuropsychological tests, measurements of oxygenated hemoglobin (HbO) using function near-infrared spectroscopy during a visual working memory task, saccadic movement measurement using an eye-tracking device, and a questionnaire assessing depressive symptoms. Results: Compared to the control group, the experimental group demonstrated significant improvements. They showed enhanced cognitive efficiency, as evidenced by improved visual working memory performance, reduced anti-saccade latency, higher scores in the Montreal Cognitive Assessment, and faster completion time in the Shape Trail Test B. In addition, significantly more participants in the experimental group showed improvement in depressive symptoms after the intervention. Conclusions: These findings provide preliminary evidence that tPBM may effectively improve neuropsychological, physiological, and psychological outcomes in individuals with MCI. This trial was registered in the Chinese Clinical Trial Registry (http://www.chictr.org.cn, registration number: ChiCTR2400090408).