Can Decreased Sleep Efficiency Miss Sleep-Disordered Breathing?
No, a study showing decreased sleep efficiency is unlikely to miss sleep-disordered breathing—in fact, decreased sleep efficiency is strongly associated with the presence of sleep-disordered breathing and may serve as an important indicator that warrants further diagnostic evaluation.
The Relationship Between Sleep Efficiency and Sleep-Disordered Breathing
Decreased sleep efficiency is not only compatible with sleep-disordered breathing (SDB) but is actually a characteristic feature of the condition. Multiple lines of evidence demonstrate that poor sleep efficiency correlates with and may indicate underlying SDB:
Evidence from Research Studies
In elderly populations, wrist actigraphy-derived poor sleep efficiency (<70%) was associated with 2.4-fold higher odds of having sleep-disordered breathing (respiratory disturbance index ≥15) in multivariable models 1. This suggests that reduced sleep efficiency, even when measured by simple actigraphy, identifies individuals at higher risk for SDB.
In patients with heart failure, those with comorbid SDB showed further decreases in sleep efficiency compared to heart failure patients without SDB, along with disruptions in sleep architecture including decreased REM and slow-wave sleep 2. This demonstrates that SDB compounds sleep disruption beyond baseline disease effects.
In elderly individuals with cognitive concerns, the cognitive impairment group showed significantly decreased sleep efficiency and an increased apnea index compared with normal subjects, with lower sleep efficiency being independently associated with increased risk of cognitive impairment 3.
The Mechanism: Sleep Fragmentation
The key mechanism linking decreased sleep efficiency to SDB is sleep fragmentation from respiratory events. Sleep-disordered breathing causes:
- Repeated arousals from apneas and hypopneas
- Increased wake after sleep onset
- Disrupted sleep architecture with reduced deep sleep stages
- Lower overall sleep efficiency
Importantly, arousal-based respiratory events are critical for diagnosis 4. The American Academy of Sleep Medicine position statement emphasizes that not including arousal-based respiratory events may lead to lack of proper OSA diagnosis or misclassification of severity. Evidence demonstrates that arousals, not just hypoxemia, better predict hypersomnia in patients with OSA 4.
Clinical Implications and Diagnostic Approach
When Sleep Efficiency is Reduced
If a sleep study shows decreased sleep efficiency, clinicians should:
Examine the respiratory event index carefully - Look beyond just the apnea-hypopnea index (AHI) to include respiratory effort-related arousals (RERAs) 4
Review arousal patterns - Determine if arousals are temporally related to respiratory events, which would indicate SDB as the cause of poor sleep efficiency
Consider full polysomnography if using home sleep testing - The ATS Duchenne Muscular Dystrophy guidelines note that "sleep-disordered breathing not associated with desaturation or CO2 retention will not be detected" by simple oximetry 5. If home testing shows poor sleep efficiency without clear SDB, in-laboratory PSG with EEG is needed to capture arousal-based events
Assess for periodic limb movements - Reduced sleep efficiency was also associated with 2.4-fold higher odds of periodic limb movement disorder 1, which can coexist with or mimic SDB
Sex Differences Matter
Women and men show different patterns with equivalent SDB severity 6. With moderate-to-severe SDB, men had lower sleep efficiency (-8.6%) and longer wake after sleep onset, while women had more insomnia symptoms. This means decreased sleep efficiency may be a more prominent feature of SDB in men, but its absence doesn't exclude SDB in women.
Common Pitfalls to Avoid
Using total recording time instead of total sleep time - When sleep efficiency is low, using recording time rather than sleep time to calculate the respiratory event index (REI) can greatly underestimate severity 7. A method to estimate total sleep time from respiratory event intervals can improve diagnostic accuracy.
Relying solely on oximetry - The Duchenne guidelines explicitly warn that overnight pulse oximetry alone will miss sleep-disordered breathing not associated with desaturation 5. Poor sleep efficiency without desaturation still requires full evaluation.
Ignoring arousal-based events - Eliminating arousal-based scoring may miss significant SDB, particularly upper airway resistance syndrome where hypoxemia is minimal but sleep fragmentation is severe 4.
Assuming decreased sleep efficiency rules out SDB - The opposite is true: decreased sleep efficiency should raise suspicion for SDB and prompt thorough respiratory event analysis.
Bottom Line
Decreased sleep efficiency does not cause you to miss sleep-disordered breathing—it is a red flag that should prompt careful evaluation for SDB. The concern should be the reverse: studies that show normal or near-normal sleep efficiency despite symptoms suggestive of SDB may warrant repeat testing or more comprehensive evaluation, as a single night may not capture the full picture 8. When decreased sleep efficiency is present, ensure arousal-based respiratory events are scored 4, use total sleep time rather than recording time for severity calculations 7, and consider full polysomnography if home testing is inconclusive 5.