Sleepiness in obstructive sleep apnea using hypopneas defined by a 3% oxygen desaturation or arousal but not by 4% or greater oxygen desaturation

Study objectives: This analysis determined the association between obstructive sleep apnea (OSA) with hypopneas defined by a 3% O₂ desaturation or arousal (3%A), but not by a hypopnea criterion of ≥ 4% (4%), and subjective sleepiness. Methods: Data were analyzed from Sleep Heart Health Study participants who had polysomnography (N = 6307) regarding OSA and subjective sleepiness scores (Epworth Sleepiness Scale, ESS). The apnea hypopnea index (AHI) was classified based on 3% only, 3%A only, and 4% definitions of hypopneas. Results: Of the 3326 participants without 4% OSA, 67.6% (n = 2247) had 3%A only OSA. The ESS score was higher in 3%A only OSA than in those without OSA (7.44 ± 4.2 vs 7.07 ± 4.3, P = 0.02). Of those without 4% OSA, 40.2% (n = 1336) had 3% only OSA. The ESS score was higher in those with 3% only OSA than those with no OSA (7.72 ± 4.3 vs 7.05 ± 4.2, P < 0.001). A linear regression model demonstrated a trend towards significance for the 3%A only AHI as an independent predictor of ESS when controlled for age, BMI, and sex (P = 0.051). The association of 3% only AHI with the ESS was stronger (P = 0.003). However, 23.3% of the participants with hypersomnia would not qualify as having OSA if arousals were excluded from the definition of OSA. Conclusion: The current study found that the presence and severity of OSA is associated with higher ESS scores in persons with 3%A only OSA. Hence, the use of the 4% hypopnea definition will result in the failure to identify and treat a significant number of individuals with OSA who have subjective sleepiness.