Rhythmic Light Therapy for Alzheimer's Disease Patients

Phase 1 - The Use of Rhythmic Light Therapy to Entrain Gamma Oscillations and the Circadian System in Patients With Alzheimer's Disease

The investigator will investigate how light delivering 40 hertz (Hz) affects subjective sleep and cognition in a controlled laboratory study. A lab study will allow the collection of electroencephalogram (EEG) data, perform cognitive tests, and observe the response in those with mild cognitive impairment (MCI) compared to a healthy control group (HC).

Participants will attend two study sessions over the course of two weeks. During both sessions, all participants will experience 10 minutes of a low-level light, followed by a data collection period which involves a sleepiness rating, an electroencephalogram (EEG) recording, and a computerized memory test. Participants will then experience either a RL or a placebo RL condition for one hour, after which there will be a second data collection.

The investigator will demonstrate the effect of 40 hertz (Hz) rhythmic light (RL) to promote gamma wave entrainment (rhythmic light [RL]) on: brain response (electroencephalography [EEG]); cognitive performance (working memory task); and subjective sleepiness (questionnaires). The study will recruit 20 adult mild cognitive impairment (MCI) patients and 20 healthy, age-matched controls (HC) to participate in this study.

Sessions will initiate with a 10-minute adaptation period to a low-level ambient light providing illuminance of 15 lux at participants' eye level on a vertical plane, followed by a pre-exposure data collection period, including Karolinska Sleepiness Scale (KSS), EEG, and a working memory task. Participants will experience either 40 Hz RL or placebo RL conditions for a duration of 1 hour, followed by the second data collection period. On the second data collection day, participants will experience the other condition, so that all participants experience both lighting conditions. The experimental sessions will start at 14:00 on each experimental day which will be separated by 1 week.

Inclusion Criteria:

• Participants must be diagnosed with amnestic mild cognitive impairment or mild Alzheimer's disease, as defined by a Montreal Cognitive Assessment (MoCA) score between 17 and 25
• For the age-matched healthy controls, participants must not be diagnosed with mild cognitive impairment or Alzheimer's disease related dementias (MoCA score above 25).
• Participants must score a 5 or less in the Pittsburgh Sleep Quality Index (PSQI)

Exclusion Criteria:

• All participants must not be taking sleeping medication or oral melatonin
• Presence of another brain disease that fully explains the dementia (extensive brain vascular disease, Parkinson's disease, dementia with Lewy bodies, traumatic brain injury, or multiple sclerosis)
• residence in a skilled nursing facility or long-term care
• Major organ failure (e.g., kidney failure)
• Uncontrolled generalized disorders such as hypertension or diabetes
• Obstructing cataracts, macular degeneration, and blindness
• Severe sleep apnea or restless leg syndrome
• History of epilepsy