Which of the following is a key indicator of sleep apnea severity in a polysomnography report?

The number of hypopneas per hour is a critical measure in assessing the severity of sleep apnea in a polysomnography report. Hypopneas are episodes of partial obstruction of the airway that lead to reduced airflow and oxygen saturation but not complete airway blockage, as occurs in apneas. The frequency of hypopneas, along with apneas, significantly contributes to the Apnea-Hypopnea Index (AHI), which is a standard metric used to classify the severity of sleep apnea: mild, moderate, or severe. A higher number of hypopneas per hour indicates a greater degree of airway obstruction and associated risks, making it a vital indicator for diagnosis and treatment planning.

Other factors mentioned, such as time spent in light sleep, overall sleep duration, and morning headache frequency, can provide some insights into the patient's sleep quality and wellbeing but do not serve as direct indicators of the severity of sleep apnea itself. They may be influenced by various factors unrelated to the severity of obstructive events during sleep. For example, while altered sleep architecture and morning headaches can occur in individuals with sleep apnea, they are not specific measures of apnea severity like the hypopnea count is.