Study on the Effect of 40 Hz Non-Invasive Light Therapy System

Inclusion Criteria: * Adult competent person, able to understand the nature of the study and give written informed consent. * Diagnosed with probable mild to moderate AD based on NIA-AA diagnostic criteria or in a prodromal stage of AD with at least one positive biomarker of AD. * Age \> 40 years. Females must be post-menopausal. * Fluent in Danish. * \> 8 years of normal school education * Pass a color-blindness test (Ishihara color test) * Have visual and auditory capabilities, and language skills necessary for neuropsychological testing. * Participants must have a designated caregiver, who is available to the participant and can provide the necessary assistance with using the LTS device and the Actigraph wearable at home and assist with clinical visits and other practical issues Exclusion Criteria: * Profound visual impairment (visual acuity \> 0.5) provided correction with spectacles, if needed * Significant abnormalities related to important parts of the brain, e.g., the visual system, prefrontal cortex, or hippocampus, or relevant lesions detected by pre-trial imaging. * Prior history of significant diseases related to the visual system or the brain. * Medication: Use of any antiepileptic drugs, neuromodulating drugs or high dose of sedatives will be excluded. * Prior history of substance abuse within the past 2 years. * Any significant systemic illness or unstable medical condition, which could lead to difficulty complying with the protocol (at the discretion of the PI)