Obstructive sleep apnea (OSA) increases risk of dementia, a relationship that may be mediated by amyloid-β (Aβ) and downstream Alzheimer disease pathology. We previously showed that OSA may impair Aβ clearance and affect the relationship between slow wave activity (SWA) and Aβ. In this study, SWA and CSF Aβ were measured in participants with OSA before and 1 to 4 months after treatment. OSA treatment increased SWA, and SWA was significantly correlated with lower Aβ after treatment. Greater improvement in OSA was associated with greater decreases in Aβ. We propose a model whereby OSA treatment may affect both Aβ release and clearance. Ann Neurol 2018 ANN NEUROL 2019;85:291–295.