How do individuals sleep around the world? Results from a single-day survey in ten countries
Introduction
Sleep troubles are a common complaint that can have a huge impact on patients' quality of life and ability to function. However, a recent review of the literature covering more than 50 studies of insomnia, based on data collected in various representative community-dwelling populations, showed that estimates of prevalence vary widely, from less than 5 to 40% [1]. Prevalence estimates can be affected by a number of factors, such as the characteristics of the population sampled, the definition of insomnia, and regional perceptions and management practices regarding sleep disorders. Few epidemiological surveys have been conducted that have used a single method to evaluate impaired sleep prevalence simultaneously in different countries. As a result, it is not clear precisely how much the prevalence of insomnia varies between global regions. It is not known whether the variability seen in studies performed to date reflects real regional differences or simply different definitions and/or methodologies.
Janson et al. [2] studied the geographic variation in sleep complaints to identify risk factors for sleep disturbances in 2202 subjects from three Northern European countries (Sweden, Iceland and Belgium) using a standardized questionnaire and sleep diaries. However, this study selected only middle-aged adults (aged 20–45 years) and did not refer to a validated insomnia scale, making regional comparisons difficult. Chevalier et al. [3] conducted a survey of severe insomnia and its effect on quality of life and healthcare consumption in five Northern European countries using a 4-item questionnaire, reporting prevalence rates of severe insomnia ranging from 4 to 22%. Finally, a telephone survey conducted by Ohayon and Roth [4] in 24,600 general population-based subjects aged ≥15 years from six European countries indicated a global insomnia prevalence of 16.8%, according to the criteria of the 4th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). However, only overall survey results were presented and no between-country comparisons were available.
The objectives of the present investigation were to describe between-country differences in both the prevalence and type of sleep disorders seen across the globe, and to gain information on how impaired sleep generally impacts daytime functioning.
Section snippets
Study design and data collection
A cross-sectional survey was conducted on International Sleep Well Day (March 21), 2002. A common standardized questionnaire was used in all countries under the guidance of local survey managers, who ensured the feasibility of data collection according to local practices. Methods used to collect data in the different regions included: China, Japan, Slovakia, South Africa—collection from a general population in public booths in various locations (e.g. streets, railway stations, shopping
Sleep habits
The average (mode) bedtime on weekdays was 11 PM, with 32.0% of individuals reporting that went to bed at this time (Table 2). The Spanish and the Portuguese reported later bedtimes (12 PM). On weekends, the average bedtime was slightly later, at 12 PM. The average (mode) waking time during the week was 6 AM, with 35.2% of participants reporting that they awoke at this time, and 31.6% at 7 AM. On weekends, the average wake-up time was 8 AM.
The mean sleep duration during the week was 454 min
Discussion
To our knowledge, this is the first international study attempting to assess sleep behaviors on the same day and with the same standardized questionnaire and scales, and covering 10 countries in four continents. Only three multi-country European studies of the general population have been published [2], [3], [4], while the World Health Organization Collaborative Study that involved 14 countries in three continents assessed the burden of sleep problems in primary care patients rather than the
Conclusion
Although there seem to be important global variations in the prevalence of insomnia, its symptoms and their management, this survey shows that about one in four individuals world-wide do not think they sleep well. Moreover, self-reported sleep problems could be underestimated in the general population. Sleep disorders seem to be considered as normal by many individuals, rather than as a real pathology that may affect their lives and, potentially, jeopardize their health. Overall, there is a
Acknowledgements
The following SLE-EP survey investigators coordinated the data collection in their respective countries: Professor R. Cluydts (Belgium), Professor M. Zhang (China), Professor T. Ohta (Japan), Dr A. Atalaia (Portugal), and Professor E. Estivill (Spain). The Sanofi-Synthelabo Group provided organizational support.
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