The application and mechanisms of photostimulation therapy in cognitive function of Alzheimer's disease patients: A scoping review

Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive cognitive decline. Clinically, it is often accompanied by a series of symptoms including memory impairment, decreased executive function, language deterioration, and neuropsychiatric abnormalities, and is the leading cause of dementia. With the accelerating aging of the population, AD has become an increasingly serious global health problem, and its disease burden is continuously rising. Data from the World Health Organization (WHO) and the Alzheimer's Disease International (ADI) show that currently more than 55 million people worldwide suffer from dementia, and this number is expected to increase to approximately 78 million by 2030 and surge to 152 million by 2050. AD is a chronic and complex disease involving multiple pathophysiological changes. Its pathogenesis is multifaceted, with the main pathological features being amyloid-beta (Aβ) plaques and neurofibrillary tangles (NFTs), as well as related astrogliosis, microglial activation, and cerebral amyloid angiopathy. These pathological changes lead to an imbalance in excitatory and inhibitory synaptic transmission in neurons, resulting in unbalanced neuronal activity, impaired neural network function, and consequently affecting the occurrence of gamma oscillations in the brain. Currently, the main drug treatment options for AD are cholinesterase inhibitors and the excitatory amino acid receptor antagonist memantine. However, these drugs do not slow down neuronal damage or stop disease progression, and may produce significant side effects, especially in the elderly. Therefore, finding an effective, safe, and low-side-effect non-pharmacological therapy is of great clinical significance. Photostimulation therapy is a non-invasive neuromodulation technique based on photobiomodulation mechanisms. It utilizes light signals of specific wavelengths, intensities, and frequencies to act on visual and non-visual photoreceptor pathways, regulating brain neural oscillations, controlling the sleep-wake cycle, and influencing neurotransmitter release and neuroplasticity, thereby improving cognitive function and behavioral symptoms. Due to its non-invasiveness, ease of operation, and good patient tolerance, this therapy has gained some application in diseases such as sleep disorders and seasonal affective disorder. In recent years, it has been gradually introduced into the auxiliary management of AD and related cognitive disorders, but systematic summaries and comprehensive evaluations are relatively lacking. Therefore, this study uses a scoping review method to summarize and analyze the current application status and existing problems of phototherapy in the cognitive function of AD patients, and to analyze its mechanisms of action, in order to provide a reference for clinical practice.