To compare the blood pressure control and cognitive responses of three groups of patients: those diagnosed with Obstructive Sleep Apnea (OSA) and treated with Continuous Positive Airway Pressure (CPAP) for at least six months, those diagnosed with OSA but not treated, and those without OSA.

This study is designed as an observational, cross-sectional investigation at the National University Hospital and Alexandra Hospital. The research aims to enroll 50 eligible patients in each of the three groups (OSA treated, OSA untreated, and non-OSA, totaling 150 participants). The recruited participants will undergo ambulatory blood pressure monitoring (ABPM) and the Montreal Cognitive Assessment (MoCA). ABPM is a widely used, noninvasive method to determine patients' blood pressure control. MoCA is a widely used screening tool designed to assess cognitive function and detect mild cognitive impairment or early signs of dementia. The MoCA evaluates various cognitive domains, including attention, memory, language, visuospatial abilities, executive functions, and orientation. It consists of a series of tasks and questions that assess different aspects of cognitive functioning, such as drawing specific shapes, recalling words or numbers, and performing simple calculations. A trained healthcare professional will administer the digital version of the MoCA, which usually takes less than 30 minutes to complete. The MoCA has been validated for use in diverse populations and has shown good sensitivity in detecting mild cognitive impairment. The maximum score on the MoCA is 30. Lower scores may indicate potential cognitive impairment.

Inclusion Criteria:

• Known OSA (AHI >/=15 events/ hour, based on sleep study) on CPAP treatment for at least six months (n=50)
• Known OSA (AHI >/=15 events/ hour, based on sleep study) NOT on CPAP treatment (n=50)
• Known non-OSA (AHI <15 events/ hour, based on sleep study) (n=50)

Exclusion Criteria:

• Known-OSA on non-CPAP treatment (e.g., mandibular advancement device, surgery, or hypoglossal nerve stimulation),
• Heart failure,
• Atrial fibrillation, or acute coronary syndrome in the prior 3 months
• Dementia (based on the medical record)
• Previous stroke
• Non-English-speaking subjects
• Pregnant and lactating women

Individuals who fulfil the inclusion criteria but not the exclusion criteria will be recruited.

Plan to make individual participant data (IPD) available to other researchers at least 5 years after study completion, subjected to final approval by the PI

At least 5 years after study completion

Plan to make individual participant data (IPD) available to other researchers at least 5 years after study completion, subjected to final approval by the PI