This multi-site study will have a sample size of n=460 divided into three groups followed for one year: 1) a CPAP adherent group (approximately n=200); 2) two control groups consisting of 2a) a CPAP non-adherent control group (approximately n=160) and 2b) a no apnea control group (n=100). This will allow us to confirm whether CPAP treatment, controlling for risk factors such as neuroimaging findings and OSA severity at baseline, predicts the primary outcome of cognitive function at 1-year follow-up. Study participants will also undergo an Amyloid PET scan, use wearable activity monitors and functional/structural MRI brain scans.