Effects of Endogenous Gamma Light Stimulation on Brain Oscillations in Cognitively-normal Older Adults

Some Alzheimer's disease (AD) studies have investigated the effects of gamma-frequency light stimulation on healthy older adults and AD patients; they have several limitations, including small sample sizes, short intervention durations, the use of flickering light (which may cause discomfort), and lack of rigorous randomized controlled trials. The aim of this study is to address these gaps by conducting a randomized, placebo-controlled, double-blind trial.

This study will recruit 52 cognitively healthy older adults aged 55 and above (N= 52). Participants will be randomly assigned to either the experimental group (N=26), receiving endogenous gamma non-flickering light stimulation, or the control sham group (N=26), receiving 70 Hz non-flickering light stimulation. The intervention will consist of 1 hour of daily stimulation, 7 days a week, for a total of 4 weeks (28 hours). Both participants and outcomes assessors will remain blinded to group allocation.

Resting-state EEG and cognitive assessments will be conducted at three time points: prior to the intervention (T1), post one-hour intervention (T2), and post one-month intervention (T3). Resting-state brainwave activity will be the primary outcome, with data collected at all three time points (T1, T2, and T3). As secondary outcomes, cognitive assessments will be administered at T1 and T3. Adverse events will also be recorded by participants immediately following each light stimulation session.

The primary aim of this study is to assess the immediate (T2 relative to T1) and long-term (T3 relative to T1) effects of endogenous gamma light stimulation on resting-state brainwave activity. Secondary objectives include evaluating cognitive performance and assessing the safety, user acceptance, and adherence to the intervention device. The results of this study will provide valuable insights into the potential of endogenous gamma light stimulation as a non-pharmacological intervention for cognitive decline in aging populations.

Inclusion criteria

• 1. Age over 55 years old.
• 2. The Cognitive Abilities Screening Instrument (CASI) score is within normal ranges adjusted for age and education.
• 3. Participants have no history of severe neurological or psychiatric disorders (such as stroke, epilepsy, depression, migraine, etc.) that could affect cognitive function.
• 4. Participants have not used drugs that may affect cognitive function (e.g., benzodiazepines, anticholinergic medications, etc.).
• 5. Participants with normal or corrected vision (e.g., glasses or contact lenses) to normal levels.
• 6. Voluntary to sign the Informed Consent Form.

Exclusion criteria

• 1. Participants enrolled in any cognitive enhancement study within the past two months.
• 2. Participants with a history of disease that could affect cognitive function (e.g., cancer, autoimmune diseases, etc.).
• 3. Pregnant, or planning to become pregnant.