Inclusion Criteria:  Participants must be diagnosed with amnestic mild cognitive impairment or mild Alzheimer's disease, as defined by a Montreal Cognitive Assessment score between 17 and 25; Have sleep disturbance indicated by a score >5 on the Pittsburgh Sleep Quality Index Sleep efficiency < 80% assessed by wearing an actigraph for 3 days Participants must reside in their homes, independent living, or assisted living facilities  Exclusion Criteria:  Participants taking sleep medication Presence of another brain disease that fully explains the dementia (extensive brain vascular disease, Parkin-son'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 severe epilepsy