[An estimation of the prevalence of excessive daytime sleepiness based on age and sex distribution of epworth sleepiness scale scores: a population based survey]

Abstract

Objectives: To describe the distribution of subjective daytime sleepiness among local residents using the Epworth Sleepiness Scale (ESS) and estimate the prevalence of excessive daytime sleepiness (EDS) in a general Japanese adult population.

Methods: Subjects consisted of all residents aged 20 years and over from a self-governing body of approximately 10,000 people located in the Hokkaido region. Questionnaires, which included a Japanese version of the ESS, were distributed and later collected by a health promoter who visited subjects' residences between October and December 2000. Subjects of the analysis were restricted to those who answered five items or more out of a total of eight items. Means and standard deviations of the ESS global score were calculated for each age group by gender. And differences with reference to sex and age were examined by ANOVA. The prevalence of EDS in the Japanese general population was estimated from this study's results by direct age adjustment using the Japanese census figures for 2000. Factors related to EDS were also examined.

Results: A total of 5,327 residents responded to the survey (86.0%). Of these, 4,412 (71.2%) were entered for analysis. The average (+/- standard deviation) ESS global score were with 5.18 +/- 3.75 (males 5.25 +/- 3.89, females 5.12 +/- 3.75). Differing significantly age, regardless of sex (P<0001). From the overall prevalence of EDS of 9.2% (males 9.6%, females 8.8%), the estimated prevalence in the Japanese general population was to be 8.9% (males 9.3%, females 8.4%). EDS was found to be related to age, sleep duration under six hours and to snoring (P=0.002, P=0.008 and P<0.001).

Conclusion: This study provided baseline data for the distribution by sex and age group of subjective daytime sleepiness in a community using the ESS and was used to generate the first ever estimated prevalence of EDS in the general Japanese adult population. The finding should prove useful for clinicians and researchers interested in (1) screening for daytime sleepiness, (2) evaluating changes between pre and post-interventions, (3) comparing epidemiological findings across studies, and lastly, (4) making of health policy. Daytime sleepiness estimated by ESS differs with the sex and age, possibly related to bio-medical and socio-medical factors. Further research is need to detail this problem.