What is the most common physiological event assessed during a sleep study for diagnosing sleep apnea?

The most common physiological event assessed during a sleep study for diagnosing sleep apnea is oxygen desaturation. This is due to the nature of sleep apnea, where the airway becomes obstructed during sleep, leading to interrupted breathing patterns. As a result, individuals may experience significant drops in oxygen saturation levels in the blood because of the repeated apneas (brief pauses in breathing), which can last from a few seconds to minutes. Monitoring these oxygen levels through pulse oximetry is a standard practice during polysomnographic studies, as it provides crucial data to help confirm the diagnosis of sleep apnea.

In contrast, heart rate variability, body temperature fluctuations, and REM sleep duration, while important physiological measures in sleep studies, are not the primary indicators used to diagnose sleep apnea. Heart rate variability is more indicative of autonomic nervous system functioning, body temperature fluctuations relate to circadian rhythms and sleep architecture, and REM sleep duration reflects sleep cycle patterns rather than direct evidence of obstructive events. Thus, oxygen desaturation is the key parameter that clearly signals the presence of apnea events.