Making Mountains Out of Molehills: Scoring Hypopnea Based on 3 and 4% Desaturation of Oxyhemoglobin

Purpose of Review This review explores recent investigations into the clinical impact of different apnea–hypopnea index (AHI) scoring criteria, namely the minimal oxygen desaturation required to score hypopnea (3% vs 4%), in patients with obstructive sleep apnea (OSA). Recent Findings Analyses of prior large cohort studies on OSA with the goal of re-interpretation of polysomnography using a 3% desaturation threshold for hypopnea have demonstrated that overall prevalence of OSA increases when using the more liberal desaturation criterion. Certain groups of patients are more likely to require a 3% desaturation rule to meet the diagnostic criteria for OSA, specifically, women, younger patients, and patients with positional-dependent OSA. The adverse clinical outcomes linked to untreated OSA diagnosed with a 4% rule persist when re-interpreting data with a 3% desaturation standard. Summary Adoption of the American Academy of Sleep Medicine (AASM) 3% desaturation recommended scoring criteria for hypopnea expectantly increases the prevalence of OSA in the general population. In turn, many more would be eligible to receive OSA treatment. OSA diagnosed using a 3% desaturation hypopnea criteria caries adverse health and behavioral risk. Access to treatment of OSA diagnosed using the 3% desaturation criteria will reduce the health burden of untreated OSA.