Habitual Sleep Duration, Unmet Sleep Need, and Excessive Daytime Sleepiness in Korean Adults

Sleep need differs between individuals, and so the same duration of sleep will lead to sleep insufficiency in some individuals but not others. The aim of this study was to determine the separate and combined associations of both sleep duration and unmet sleep need with excessive daytime sleepiness (EDS) in Korean adults.

The participants comprised 2,769 Korean adults aged 19 years or older. They completed questionnaires about their sleep habits over the previous month. The question regarding sleep need was "How much sleep do you need to be at your best during the day?" Unmet sleep need was calculated as sleep need minus habitual sleep duration. Participants with a score of >10 on the Epworth Sleepiness Scale were considered to have EDS.

The overall prevalence of EDS was 11.9%. Approximately one-third of the participants (31.9%) reported not getting at least 7 hours of sleep. An unmet sleep need of >0 hours was present in 30.2% of the participants. An adjusted multivariate logistic regression analysis revealed a significant excess risk of EDS in the groups with unmet sleep needs of ≥2 hours [odds ratio (OR), 1.80; 95% confidence interval (CI), 1.27-2.54] and 0.01-2 hours (OR, 1.42; 95% CI, 1.02-1.98). However, habitual sleep duration was not significantly related to EDS.

EDS was found to be associated with unmet sleep need but not with habitual sleep duration when both factors were examined together. We suggest that individual unmet sleep need is more important than habitual sleep duration in terms of the relation to EDS.