Pitfalls of AHI system of severity grading in obstructive sleep apnoea

Abstract

Obstructive sleep apnoea (OSA) is the major underlying co-morbidity in many of the noncommunicable diseases (NCD) due to obesity as a common risk factor. Incidence and prevalence of OSA is on the constant rise ever since this entity came to forefront three decades ago. Precise treatment of underlying OSA is extremely important in major NCDs like diabetes mellitus, hypertension, endocrine disorders and vascular diseases. OSA is subcategorized in to mild, moderate and severe based of apnoea-hypopnea index (AHI). Based on the severity grading, treatment of OSA ranges from life style modifications to oral appliances, continuous positive airway pressure (CPAP) and surgeries. AHI system of severity grading in OSA has several inherent shortcomings and using AHI system for severity grading as the holy grail is likely to be counter-productive. AHI system equates apnoea and hypopnea as equal events, whereas physiological effects vary significantly. AHI system does not account duration of apnoea or body position during apnoeic events. We discuss at length the pitfalls of AHI system of severity grading in OSA.

A clinical review of obstructive sleep apnea

“…An AHI of 5 to 14.9 is considered mild OSA, 15 to 29.9 is moderate, and more than 30 is severe 13. Although AHI remains the AASM's metric of choice to stratify OSA severity, the simplicity of the calculation may under- or overestimate disease severity 16. Calculating the frequency of apneas and hypopneas, as is done with AHI calculation, does not account for other measures that have been demonstrated to have a significant effect on patient outcomes such as cardiovascular disease and all-cause mortality.…”

“…Calculating the frequency of apneas and hypopneas, as is done with AHI calculation, does not account for other measures that have been demonstrated to have a significant effect on patient outcomes such as cardiovascular disease and all-cause mortality. These measures include differentiating apneas from hypopneas, duration of apneic or hypopneic events, severity and duration of oxygen desaturation, heart rate variability, awakenings, periodic limb movements, and daytime sleepiness 16. The International Classification of Sleep Disorders has adopted the respiratory disturbance index to diagnose OSA 17.…”

“…13 Although AHI remains the AASM's metric of choice to stratify OSA severity, the simplicity of the calculation may under-or overestimate disease severity. 16 Calculating the frequency of apneas and hypopneas, as is done with AHI calculation, does not account for other measures that have been demonstrated to have a significant effect on patient outcomes such as cardiovascular disease and all-cause mortality. These measures include differentiating apneas from hypopneas, duration of apneic or hypopneic events, severity and duration of oxygen desaturation, heart rate variability, awakenings, periodic limb movements, and daytime sleepiness.…”

“…These measures include differentiating apneas from hypopneas, duration of apneic or hypopneic events, severity and duration of oxygen desaturation, heart rate variability, awakenings, periodic limb movements, and daytime sleepiness. 16 The International Classification of Sleep Disorders has adopted the respiratory disturbance index to diagnose OSA. 17 This index includes apnea, hypopnea, and respiratory effort-related arousals per hour of sleep.…”

Airway Collapsibility during Drug‐Induced Sleep Endoscopy Relates with Clinical Features of Obstructive Sleep Apnea

“…In current clinical practice, OSA severity is defined by the apnea–hypopnea index (AHI) and treatment response by reductions in AHI 12 . However, AHI does not consistently correlate with symptomatology, fully characterize disease burden, or reliably predict treatment response 13–15 . Validated PROMs such as the Epworth Sleepiness Scale (ESS) characterize symptoms amongst patients with OSA 16–21 .…”