What are the clinical characteristics of REM (Rapid Eye Movement)-predominant sleep apnea?

Clinical Characteristics of REM-Predominant Sleep Apnea

REM-predominant obstructive sleep apnea (REM-OSA) is characterized by respiratory events that occur primarily during REM sleep, with longer and more desaturating events compared to those in NREM sleep, and is more prevalent in women than men, typically occurring in the context of mild-to-moderate OSA. 1

Definition and Diagnostic Criteria

• REM-predominant OSA is defined as having an apnea-hypopnea index (AHI) REM/NREM ratio of at least 2, with a minimum REM sleep time of 30 minutes 2
• Polysomnographic characteristics include respiratory events that are concentrated during REM sleep phases, which typically occur more in the second half of the night 1
• The diagnosis requires time-synchronized video polysomnography to confirm the pattern of respiratory disturbances predominantly during REM sleep 3

Pathophysiological Mechanisms

• During REM sleep, the upper airway is more prone to collapse due to REM sleep atonia, leading to increased frequency and severity of obstructive events 1
• Thoracoabdominal asynchrony occurs during REM sleep due to loss of rib cage stabilization from inspiratory intercostal muscle inhibition 4
• Patients with respiratory muscle weakness characteristically show dips in oxygen saturation related specifically to periods of REM sleep 3

Clinical Presentation

• Patients with mild REM-OSA are twice as likely to experience excessive daytime sleepiness compared to those with NREM-OSA (odds ratio 2.16) 2
• The severity of respiratory disturbance during REM sleep is greater than during NREM sleep, with longer apnea-hypopnea episodes 5
• Despite having a lower overall AHI, patients with REM-OSA may experience similar levels of daytime sleepiness as those with non-sleep-stage-dependent OSA 1

Demographic and Clinical Associations

• REM-OSA is more common in women than men 1, 6
• Higher body mass index (BMI) is significantly associated with REM-predominant OSA 6
• REM-OSA typically occurs in the context of mild-to-moderate OSA based on the total AHI 1
• Patients with REM-OSA are more likely to be obese (42.5% vs. 24.4%) compared to those with non-stage specific OSA 6

Clinical Significance and Consequences

• REM-OSA is associated with systemic hypertension and increased cardiometabolic risk 1
• In patients with coronary artery disease, REM-AHI is inversely associated with mental health quality of life scores 6
• Respiratory events during REM sleep are usually longer and cause more significant oxygen desaturation than events during NREM sleep 1, 5
• The lowest oxygen saturation (LSaO2) is typically lower during REM stage than during NREM stage 5

Treatment Considerations

• Continuous positive airway pressure (CPAP) treatment for REM-OSA should be longer than the standard 4 hours of use, since REM sleep occurs mostly during the second half of the night 1
• Patients with REM-OSA often show poor adherence to CPAP therapy 1
• CPAP therapy can effectively manage both obstructive and central components of REM-predominant sleep apnea, as demonstrated in case reports 7
• Due to the impact on daytime sleepiness, a lower treatment threshold may be warranted to include symptomatic patients with mild REM-OSA 2

Special Clinical Scenarios

• In patients with chronic lung disease of infancy and childhood, episodes of desaturation with SaO2 values less than 90% are more common during REM sleep than during non-REM sleep 3
• In elderly individuals, normal aging is associated with decreased REM sleep, which can further impact the presentation of REM-OSA 8
• Medications, particularly serotonergic antidepressants, can induce or exacerbate REM sleep abnormalities and potentially affect breathing patterns during REM sleep 4, 8

Clinical Pitfalls and Caveats

• REM-OSA may be underdiagnosed if sleep studies are too short or if insufficient REM sleep is captured during the recording 2
• The clinical significance of REM-OSA may be underestimated in patients with mild overall AHI, despite significant daytime symptoms 2
• In patients with respiratory muscle weakness, some apneas that appear to be central during REM sleep may actually be obstructive, with incorrect classification due to failure of external sensors to detect chest wall movements of reduced amplitude 3