Predictors of objective sleep tendency in the general population

Study Objectives: Daytime sleepiness is a pervasive problem that is associated with a significant public-health burden. Although self-reported measures of daytime sleepiness may be useful in identifying at-risk individuals, there is significant controversy because there are no population-based data relating subjective and objective measures of daytime sleep tendency. The aims of this study were to examine the associations between the Multiple Sleep Latency Test (MSLT), an objective measure of daytime sleep tendency, and self-reported information on the Epworth Sleepiness Scale (ESS) and nighttime sleep duration in the general population. Design: Cross-sectional study. Setting and Participants: Population-based sample of 261 women and 371 men, mean age of 50.8 years, enrolled in the Wisconsin Sleep Cohort Study. Measurements: MSLT, ESS, and self-reported sleep duration prior to the MSLT. Results: Using survival analysis to model the time to sleep onset during the MSLT, we found that individuals with an intermediate (6-11) and high (≥12) ESS score had a 30% and 69% increase in risk for sleep onset during the MSLT, respectively, compared to individuals with a low ESS score (≤5). A dose-response relationship between self-reported duration of nighttime sleep and objective sleep tendency was also observed. Compared to individuals reporting more than 7.50 hours of sleep (highest fertile), individuals reporting 6.76 to 7.50 hours and less than 6.75 hours (lowest tertile) had a 27% and 73% increase in risk for sleep onset during the MSLT, respectively. Conclusions: Subjective reports of daytime sleep tendency on the ESS and the duration of nighttime sleep are associated with the results of the MSLT in the general population.