This study will conduct 3 intervention trials with 44 different participants in each trial, with 22 participants will undergo in-laboratory overnight polysomnograms (PSGs) at one night of medication intervention, and the other 22 at taking placebo (contained starch) 1 h before sleep. Three medication regimens will be tested: (1) atomoxetine 80mg combined with oxybutynin 5mg; (2) venlafaxine 37.5mg; and (3) oxybutynin 5mg combined with trazodone 100mg. Endotypic traits will be estimated using the Phenotyping Using Polysomnography method. The primary outcome is the change in apnea-hypopnea index, and secondary outcomes include endotypic traits and sleep parameters.

Inclusion Criteria:

• apnea-hypopnea index ≥ 15 hr-¹

Exclusion Criteria:

• the presence of pulmonary, cardiac, neurologic, or other active severe medical or psychiatric diseases
• current use of continuous positive airway pressure therapy
• use of drugs that might interact with the investigational medication or known to affect sleep during the trial or 1 month before the study
• known allergy to the investigational medication
• current smoking
• heavy alcohol drinking (male > 14 drinks and women >7 drinks per week)
• pregnant or lactating
• periodic limb movement index > 15hr-1
• the presence of sleep-related hypoventilation