Understanding Circadian Responses to Light in Persons With Mild Cognitive Impairment

Understanding Circadian Responses to Light in Persons With Mild Cognitive Impairment and Alzheimer's Disease

The purpose of this research study is to investigate the relationship between light, the thickness of the pigment at the back of your eye, melatonin levels, and memory. The study will investigate whether changing light distribution pattern from "on-axis"' (i.e., directed along the eye's visual axis to the fovea) to "off-axis" (i.e., directed on the periphery of the eye's visual axis) impact melatonin suppression in 24 mild cognitive impairment participants and 24 healthy, age-matched controls.

Eligible enrolled subjects will be exposed to 4 different lighting conditions in addition to one dark control condition. There will be 5 study session and each one will last for 90 minutes and will be separated by one week. Subjects will collect 3 saliva samples, each one 30 minutes apart for melatonin levels during each study session.

Inclusion Criteria:

• mild cognitive impairment
• age matched healthy control
• macular pigment density either < 0.3 or > 0.5

Exclusion Criteria:

• extensive brain vascular disease
• Parkinson's disease
• bipolar disorder
• seasonal depression
• diabetes
• high blood pressure
• obstructing cataracts
• macular degeneration
• diabetic retinopathy
• use of melatonin supplements
• use of beta blockers
• use of sleep medications
• use of antidepressant medication