Association between the Epworth Sleepiness Scale and the multiple sleep latency test in a clinical population

Background: Excessive daytime sleepiness can be evaluated with both subjective and objective tests. Objective: To examine the association between Epworth Sleepiness Scale scores and sleep latency on the multiple sleep latency test. Design: Case series. Setting: Referral sleep disorders center. Patients: 102 consecutive patients evaluated for excessive daytime sleepiness. Measurements: Epworth Sleepiness Scale scores and mean sleep latency on the multiple sleep latency test. Results: No significant association was seen between Epworth scores and mean sleep latency (Pearson correlation, -0.17 [95% CI, -0.35 to 0.03]; P = 0.09) (analysis of variance, P = 0.13). The mean Epworth score did not differ in three groups of patients who were defined by mean sleep latency as having normal sleep latency (>10 minutes), moderate sleep latency (5 to 10 minutes), or severe sleep latency (<5 minutes) (analysis of variance, P = 0.13). Conclusions: No statistically or clinically significant association was seen between Epworth scores and mean sleep latency. The subjective Epworth Sleepiness Scale and the objective multiple sleep latency test may evaluate different, complementary aspects of sleepiness.