Original ArticleEpidemiology of sleep-related complaints associated with sleep-disordered breathing in Bangkok, Thailand
Introduction
The prevalence of sleep-disordered breathing (SDB) is well described in Caucasians [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15]; however, few epidemiologic studies address the prevalence of and risk factors related to SDB in Asian populations [16], [17], [18], [19], [20], [21], [22].
In the Caucasian population, it is estimated that more than 60% of adults occasionally snore [23] and 40% regularly snore [24]. SDB, as defined by an apnea–hypopnea index (AHI) greater than five events per hour, occurs in approximately 10% of females and 25% of males, and 2% and 4%, respectively, experience sleepiness associated with an increased AHI [4], [6]. When present, excessive daytime sleepiness (EDS) imposes a substantial burden on quality of life, morbidity and mortality in patients with SDB [25] because it is a known risk factor for motor vehicle [26], [27] and work-related accidents and can result in significant psychological and cognitive deficits [28], [29].
Snoring has been shown to be associated with excessive sleepiness [4], [30]. Gottlieb and colleagues [31] showed an increased Epworth Sleepiness Scale (ESS) score in snoring men and women regardless of apnea–hypopnea frequency and found that snoring is associated with excessive sleepiness independent of the effect of an abnormal respiratory disturbance index (RDI). They found a dose–response relationship between snoring and sleepiness, with increasing sleepiness associated with increasing frequency and intensity of snoring. This association between snoring and sleepiness was observed in both men and women. Similarly, Young and colleagues [4] found that snorers with RDI < 5 were substantially more likely to report excessive daytime sleepiness or awakening unrefreshed than were nonsnorers with RDI < 5. The magnitude of the relationship between snoring and sleepiness in this study suggests that snoring-related sleepiness may have an important public impact. These findings suggest that even the mildest form of abnormal sleep-related breathing, i.e., snoring without an abnormal RDI, may cause sleepiness.
This epidemiologic study investigates the prevalence of sleep-related complaints suggestive of SDB in individuals living in Bangkok, aged 16 years and older, and identifies important clinical and demographic predictors of these complaints. This study looks primarily at snoring and EDS since there is evidence to suggest that snoring-related sleepiness, independent of SDB, may have an important impact on public health.
Section snippets
Study subjects
The National Statistical Office of Thailand (TNSO) selected individuals based on results of the year 2000 Census. Selected individuals were matched for age, gender, education and professional activities to provide a representative sample of the 5,216,100 individuals aged 16 years and older in the Bangkok population. Furthermore, potential replacement subjects were selected in case first choice interviewees were not available. The study was performed between May and July 2007.
A stratified
Demographics
The total sample population consisted of 4680 subjects. The male-to-female ratio of respondents was 83:100, compared to 88:100 in the Bangkok population. There were no significant differences in age distribution, education, marital status, and employment status between males and females (Table 1).
Prevalence
Among the 4680 subjects, 202 (4.3%) complained of snoring and EDS greater than 3 days/nights per week for at least 3 months. These complaints were significantly more common in men (112/2118; 5.3%)
Discussion
This is the first epidemiological study to investigate sleep disorders in the Thai population. This study demonstrates a high prevalence of sleep-related complaints associated with sleep-disordered breathing, consistent with those reported in many other countries [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19]. Risk factors and symptomology overlap with those found in Caucasians populations, but important differences were found as well.
Conclusion
Significant sleep-related complaints associated with sleep-disordered breathing and health morbidities exist in the Thai population. The results of our study show some similarities in prevalence and risk factors for SDB to Caucasian populations, but also show important differences. These differences may be associated with differences in naso-maxillary anatomical features leading to smaller upper airways in the Asian population. Comparison of findings in different populations may help clarify
Acknowledgements
This study was funded by the Thailand Research Fund (TRF) and the Commission on Higher Education (CHE). The authors would like to thank the National Statistical Office of Thailand (TNSO) for the random sampling and the data collecting processes they provided.
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