Purpose of review <p>Obstructive sleep apnea (OSA) that occurs predominantly during rapid eye movement (REM) sleep, termed REM-OSA, is increasingly recognized as a stage-specific form of OSA with distinct physiology and clinical relevance. Despite sometimes lower overall apnea–hypopnea index (AHI) values, REM-OSA has been associated with significant adverse outcomes. This review summarizes current evidence on the cardiovascular, cognitive, and metabolic consequences of REM-OSA, along with treatment considerations.</p> Recent Findings <p>REM-OSA is independently associated with non-dipping hypertension, increased cardiovascular risk, and subclinical atherosclerosis. Cognitive deficits, including impaired memory consolidation, reduced attention, and mood disturbances, are linked to disrupted REM sleep. Metabolically, REM-OSA is associated with insulin resistance, glucose dysregulation, and systemic inflammation. While continuous positive airway pressure (CPAP) therapy remains the standard treatment, its effectiveness for REM-specific events may be reduced in some patients, highlighting the need for individualized approaches. Alternative therapies, such as oral appliances, pharmacologic agents, and interventions targeting upper airway muscle tone, have been explored, though further research is needed to establish their role in REM-OSA.</p> Summary <p>REM-OSA is an underrecognized but clinically significant form of OSA with distinct health implications. Standardized definitions, refined diagnostic criteria, and tailored treatment strategies are essential to improve clinical outcomes. Longitudinal studies are also needed to clarify the long-term impact of REM-OSA and evaluate the effectiveness of emerging therapies.</p>