How do individuals sleep around the world? Results from a single-day survey in ten countries
To describe between-country differences in both the prevalence and type of sleep disorders seen across the globe, and to provide information on how impaired sleep impacts daytime functioning. The study is a large-scale, global cross-sectional survey conducted on International Sleep Well Day (March 21), 2002. A standardized questionnaire was used in 10 countries under the guidance of local survey managers. In addition, the Athens Insomnia Scale (AIS) and the Epworth Sleepiness Scale (ESS) were completed. Subjects included in the study were adults from 10 countries representing different continents with clear variations in lifestyle. The total number of questionnaires collected was 35,327. Overall, 24% of subjects reported that they did not sleep well. According to self-assessments using the AIS, 31.6% of subjects had 'insomnia', while another 17.5% could be considered as having 'sub-threshold insomnia'. According to ESS scores, 11.6% of subjects were found to be 'very sleepy' or 'dangerously sleepy' during the day. Although there seem to be important global variations in the prevalence of insomnia, its symptoms and their management, about one in four individuals do not think they sleep well. Moreover, self-reported sleep problems could be underestimated in the general population. Overall, there is a need for increased awareness of the importance of disturbed sleep and the improved detection and management of sleep disorders.