Correlating subjective and objective sleepiness: revisiting the association using survival analysis

Area of Science:

• Sleep Medicine
• Clinical Neurophysiology

Background:

• The Epworth Sleepiness Scale (ESS) and multiple sleep latency test (MSLT) are standard measures for subjective and objective sleepiness.
• The relationship between ESS scores and objective sleep latency, and the optimal ESS threshold for identifying sleepiness, require further investigation.

Purpose of the Study:

• To examine the association between ESS scores and MSLT average sleep latency using survival analysis.
• To determine if patient factors influence this association.
• To evaluate the predictive utility of individual ESS questions and identify an optimal ESS threshold for objective sleepiness.

Main Methods:

• Cross-sectional study involving 675 patients referred for polysomnography and MSLT.
• Survival analysis techniques were employed to assess the association between ESS scores and MSLT sleep latency.

Main Results:

• A significant association was found between ESS scores and MSLT average sleep latency, with higher ESS scores correlating with shorter sleep latencies.
• An ESS score of 13 or greater optimally predicted an average MSLT sleep latency of less than 8 minutes.
• Most ESS questions were predictive of objective sleepiness, with some variations based on patient factors.

Conclusions:

• Survival analysis clearly demonstrates the association between ESS and MSLT average sleep latency.
• An ESS score of 13 or higher is an effective threshold for predicting objective sleepiness, surpassing previously used clinical cutoffs.
• The ESS is a simple, cost-effective tool for identifying individuals at risk of excessive daytime sleepiness.