The purpose of this study is to compare the results of two different sleep tests in Alzheimer's patients with no symptoms or early symptoms. Participants will undergo two simultaneous sleep tests (polysomnography) in a sleep laboratory for two nights and one sleep test at home for three nights. For each participant, the study will last at least a week and will last up to three months.

Inclusion Criteria:

• Have mild cognitive impairment, subjective memory complaints, or normal cognition.
• Evidence of the presence of Alzheimer's pathology as measured by amyloid positron emission tomography (PET), cerebrospinal fluid biomarkers (amyloid beta and tau), or blood biomarkers.
• Montreal Cognitive Assessment (MoCA) score of 24 or greater.
• Clinical Dementia Rating Scale (CDR) global score of 0 or 0.5.
• Able to provide signed informed consent.
• On stable medications (including those for Alzheimer's disease) for 30 days before the first recording night of Study Period 1, and willing to remain on stable therapy during the study.
• Must have a study partner who knows the participant well and can accompany the participant at visits where informant-rated scales are administered.

Exclusion Criteria:

• Severe illness that in the investigator's judgement would adversely affect the participant's participation in the study.
• Skin illness that may interfere with study assessments.
• Has a pacemaker or implantable cardioverter defibrillator.
• Diagnosed with a sleep disorder.
• Has irregular circadian patterns (works night shifts, etc.).
• Is pregnant or lactating/breastfeeding at time of screening.
• Use of sleep aid medications (such as melatonin, Ambien, Lunestra) or other medications or substances that could affect sleep (alcohol, cannabinoids, or opioids) on nights of in-clinic and at-home recordings.
• Currently enrolled in another clinical study involving an investigational product or other type of medical research judged not to be scientifically or medically compatible with this study.
• People who habitually spend less than 5 hours in bed per night.
• No alcohol will be allowed at least 24 hours before the use of the EEG and throughout the clinical assessment period.

Singaporean age 55-85 with mild memory complaints or MCI who are otherwise healthy.