Inclusion Criteria:
- Male or female.
- Any race or ethnicity.
- Participants must be age ≥ 65 years and able to sign informed consent.
- Global Clinical Dementia Rating (CDR) 0.
- Willing and able to undergo study procedures.
Exclusion Criteria:
- History or reported symptoms suggestive of restless legs syndrome, narcolepsy, or parasomnia.
- STOP-Bang score >6 for participants without PAP.
- Untreated sleep apnea AHI>15
- Poorly treated sleep apnea due to noncompliance or an AHI ≥ 10.
\- PAP compliance is defined as ≥ 4 hours per night >70% of the nights.
- Plasma p-Tau217/np-Tau217% <2.5
- Stroke.
- History of renal impairment
- Defined as older adult patients with markers of kidney damage or eGFR < 45.0 ml/min/1.73m2.
- Normal Limits ≥ 45.0 mL/min/1.73m2
- History of hepatic impairment
- AST and/or ALT ≥ 2X upper limit of normal (ULN).
- Normal Limits: AST 11-47 IU/L and ALT 6-53 IU/L
- HIV/AIDS.
- History of substance abuse or alcohol abuse in the preceding 6 months.
- Regular alcohol consumption 3 or more days a week over the last 6 months. Regular alcohol consumption is defined as having more than 2 alcoholic beverages within 3 hours of bedtime. Participants that agree to reduce alcohol consumption during the study may not be excluded.
- History of presence of any clinically significant medical condition, behavioral or psychiatric disorder, or surgical history based on medical record or participant report that could affect the safety of the participant or interfere with study assessments or in the judgement of the Principal-Investigator (PI) if participant is not a good candidate.
- Has any medical condition that, in the PI's or study team investigator's opinion, could increase risk to the participant, limit the participant's ability to tolerate the research procedures, or interfere with the collection/analysis of the data. Potential medical conditions that will be exclusionary at the PI's or study team investigator's discretion:
- Cardiovascular disease requiring medication except for controlled hypertension.
- Pulmonary disease.
- Type I diabetes.
- Neurologic or psychiatric disorder requiring medication.
- Untreated depression
- Tobacco use.
- Use of sedating medications.
- Use of medications that interact with lemborexant (if cannot be discontinued).
- Abnormal safety labs.
- History of current suicidal ideations.
- Inability to speak and understand English.
- Currently pregnant or breast-feeding.
- In the opinion of the PI, the participant should be excluded due to an abnormal physical examination.
- Must not have participated in any clinical trial involving a study drug or device within the 30-days prior to study enrollment.
- Must not participate in another drug or device study prior to the end of this study participation.
Optional assessment exclusion criteria:
• Contraindication to lumbar puncture (anticoagulants; bleeding disorder; allergy to lidocaine or disinfectant; prior central nervous system or lower back surgery).