This study is a randomized controlled trial with two phases: pre-trial and formal trial. The pre-trial will include 5 participants to observe the 4-week adherence (≥4 hours/night) and safety (adverse event rate) of the iNAP device. For the formal trial, 60 patients with MCI and moderate-to-severe OSA will be stratified and block randomized (by baseline AHI levels: 15-30 events/h vs >30 events/h) into either the iNAP intervention group (using the device nightly for 24 weeks) or the control group (receiving only sleep hygiene guidance). The primary outcome is the change in MoCA scores from baseline at week 24. Secondary outcomes include AHI reduction rate, sleep efficiency, plasma Aβ42/Aβ40 ratio, cognitive assessments, and brain imaging indicators. Follow-up visits will occur at baseline, week 12, and week 24 to monitor cognitive function, sleep parameters, and safety.

Inclusion Criteria:

1. Aged between 50 and 75 years, regardless of gender.
2. Diagnosed with moderate-to-severe obstructive sleep apnea (OSA) via polysomnography (PSG), with an Apnea-Hypopnea Index (AHI) ≥ 15 events/hour.
3. Neuropsychological assessment consistent with mild cognitive impairment (MCI), defined as a Clinical Dementia Rating (CDR) of 0.5 and a Montreal Cognitive Assessment (MoCA) score between 20 and 26.
4. Successful completion of the iNAP device adaptation test (no significant oral discomfort, nausea, or other adverse reactions after 30 minutes of wear).
5. If using cognitive-enhancing medications (e.g., cholinesterase inhibitors, memantine), stable doses must be maintained for at least 12 weeks prior to baseline.
6. Voluntary signing of the informed consent form and willingness to comply with follow-up procedures.

Exclusion Criteria:

1. History of allergy to silicone components of the iNAP device. Severe nasal obstructive diseases (e.g., nasal polyps, moderate-to-severe chronic rhinitis) that impair nasal breathing function.
2. Acute cardio-cerebrovascular events (e.g., myocardial infarction, cerebral infarction) or acute exacerbation of moderate-to-severe lung diseases (e.g., COPD exacerbation) within the past 6 months.
3. Comorbidities with other sleep disorders (e.g., primary insomnia, narcolepsy, restless legs syndrome) that may interfere with OSA assessment.
4. Diagnosis of central nervous system diseases (e.g., epilepsy, sequelae of encephalitis) or severe mental illness (e.g., schizophrenia, major depression with SDS ≥ 63 points).
5. Severe aphasia or physical disability precluding completion of neuropsychological assessments.
6. Presence of consciousness disturbance from any cause.
7. Current diagnosis of depression or psychiatric disorders.
8. History of alcoholism, drug addiction, or neurological diseases known to cause cognitive impairment (e.g., traumatic brain injury, epilepsy, encephalitis, normal pressure hydrocephalus).
9. Concurrent participation in other clinical trials.