REM sleep obstructive sleep apnoea (REM OSA) is a type of sleep apnoea that occurs predominantly during rapid eye movement (REM) sleep. It is more commonly found in women with mild to moderate OSA and is associated with systemic hypertension. REM OSA is characterized by longer and more severe respiratory events during REM sleep compared to non-REM (NREM) sleep. The apnoea-hypopnoea index (AHI) is used to assess the severity of OSA, with REM OSA typically occurring when the AHI is within the normal range. The pathophysiology of REM OSA involves reduced ventilatory drive and increased susceptibility to respiratory events during REM sleep, which can lead to oxygen desaturation and increased cardiovascular risk. REM OSA is often underdiagnosed because it may not meet the criteria for OSA based on overall AHI. However, it is associated with significant health consequences, including hypertension, increased cardiovascular risk, and metabolic abnormalities. Treatment with continuous positive airway pressure (CPAP) is recommended, but adherence is often poor, particularly in patients with REM OSA. Alternative non-CPAP treatments are being explored, but data are limited. Studies have shown that REM OSA is more prevalent in women than in men and is more common in younger individuals. It is also associated with a higher risk of cardiovascular events, particularly in those with severe REM OSA. The role of REM OSA in the development of metabolic syndrome and its impact on cardiometabolic health is an area of ongoing research. The management of REM OSA remains challenging due to the lack of a standardized definition and the difficulty in obtaining objective data. Current guidelines recommend CPAP therapy for at least 4 hours per night, but this may not be sufficient for patients with REM OSA, as REM sleep occurs in the latter half of the night. Further research is needed to clarify the clinical significance of REM OSA, its impact on health outcomes, and the effectiveness of alternative treatments. The need for a standardized definition and more long-term studies is emphasized to improve the understanding and management of REM OSA.REM sleep obstructive sleep apnoea (REM OSA) is a type of sleep apnoea that occurs predominantly during rapid eye movement (REM) sleep. It is more commonly found in women with mild to moderate OSA and is associated with systemic hypertension. REM OSA is characterized by longer and more severe respiratory events during REM sleep compared to non-REM (NREM) sleep. The apnoea-hypopnoea index (AHI) is used to assess the severity of OSA, with REM OSA typically occurring when the AHI is within the normal range. The pathophysiology of REM OSA involves reduced ventilatory drive and increased susceptibility to respiratory events during REM sleep, which can lead to oxygen desaturation and increased cardiovascular risk. REM OSA is often underdiagnosed because it may not meet the criteria for OSA based on overall AHI. However, it is associated with significant health consequences, including hypertension, increased cardiovascular risk, and metabolic abnormalities. Treatment with continuous positive airway pressure (CPAP) is recommended, but adherence is often poor, particularly in patients with REM OSA. Alternative non-CPAP treatments are being explored, but data are limited. Studies have shown that REM OSA is more prevalent in women than in men and is more common in younger individuals. It is also associated with a higher risk of cardiovascular events, particularly in those with severe REM OSA. The role of REM OSA in the development of metabolic syndrome and its impact on cardiometabolic health is an area of ongoing research. The management of REM OSA remains challenging due to the lack of a standardized definition and the difficulty in obtaining objective data. Current guidelines recommend CPAP therapy for at least 4 hours per night, but this may not be sufficient for patients with REM OSA, as REM sleep occurs in the latter half of the night. Further research is needed to clarify the clinical significance of REM OSA, its impact on health outcomes, and the effectiveness of alternative treatments. The need for a standardized definition and more long-term studies is emphasized to improve the understanding and management of REM OSA.