Eligibility Criteria:
Inclusion Criteria:
1. Informed consent
2. Age 30-65 years
3. Newly diagnosed OSA (full-night in-laboratory polysomnography \[PSG\] with AHI ≥ 15 events per hour)
4. Adherence to CPAP treatment
5. No participation in any other clinical trial in the past 3 months
6. Able to accomplish relevant tests and follow-up
Exclusion Criteria:
1. Severe systemic diseases (e.g., cardiac, hepatic, and renal failure)
2. Psychiatric conditions (e.g., depression, mania, schizophrenia)
3. Neurological diseases (e.g., head trauma, brain tumor, epilepsy, stroke, transient ischemic attack, coma)
4. Sleep disorders other than OSA (narcolepsy, insomnia, chronic sleep deprivation, rapid eye movement \[REM\] behavior disorder and restless legs syndrome, central sleep apnea or obesity hypoventilation syndrome)
5. Alcoholism, drug addiction, use of psychotropic drugs, sedatives, or narcotics
6. Prior therapy for OSA (i.e., CPAP, upper airway surgery, oral appliance)
7. Minimum Mental State Examination (MMSE)\< 24
8. Left-handed
9. MRI contraindications (e.g., claustrophobic or metal implantation)
10. Gastrointestinal surgery during the last year, except for appendicitis and hernia surgery
11. Pregnancy
12. Use of intestinal flora regulator (e.g., antibiotics or probiotics) in the previous 8 weeks
13. Medical treatment for cholecystitis, gallstones, gastrointestinal ulcers, urinary tract infection, acute pyelonephritis, or cystitis in the past 3 months
14. Infectious diseases, such as tuberculosis, acquired immune deficiency syndrome
15. Commercial drivers or people deemed to be at risk of driving -related accidents
16. Deemed by the researchers to be suitable for this trial