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Clinical Investigations: SLEEP |

A Community Study of Sleep-Disordered Breathing in Middle-aged Chinese Men in Hong Kong* FREE TO VIEW

Mary S. M. Ip, MD, FCCP; Bing Lam, MRCP; Ian J. Lauder, PhD; Kenneth W. T. Tsang, MD, FCCP; Ka-fai Chung, MRCPsych; Yuk-wan Mok, BSc; Wah-kit Lam, MD, FCCP
Author and Funding Information

*From the Departments of Medicine (Drs. Ip, Lam, Tsang, and Lam, and Ms. Mok), Statistics and Actuarial Science (Dr. Lauder), and Psychiatry (Dr. Chung), The University of Hong Kong, Hong Kong, SAR, China.

Correspondence to: Mary S. M. Ip, MD, FCCP, Department of Medicine, The University of Hong Kong, 4/F, Professorial Block, Queen Mary Hospital, Pokfulam Rd, Hong Kong SAR, China; e-mail: msmip@hkucc.hku.hk



Chest. 2001;119(1):62-69. doi:10.1378/chest.119.1.62
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Background: Sleep-disordered breathing (SDB) in Asian populations is being increasingly recognized. This study investigated the prevalence of SDB in Chinese middle-aged office-based male workers in Hong Kong.

Methods: Sleep questionnaires were distributed to 1,542 men (age range, 30 to 60 years), and 784 questionnaires were returned. Subsequently, full polysomnographic (PSG) examinations were conducted in 153 questionnaire respondents. Subjects with an apnea-hypopnea index (AHI) ≥ 5 were recalled for clinical assessment.

Results: Questionnaire respondents were similar in age and body mass index (BMI) to the general community in the target age range and gender. Habitual snoring was reported by 23% of this cohort and was associated with excessive daytime sleepiness (EDS), hypertension, witnessed abnormal breathing pattern, BMI, and leg movements during sleep. Allowing for subject bias in undergoing PSG, the estimated prevalence of SDB and obstructive sleep apnea syndrome (OSAS) (defined as SDB in the presence of EDS) at various AHI cutoff threshold values was 8.8% and 4.1% (AHI ≥ 5), 6.3% and 3.2% (AHI≥ 10), and 5.3% and 3.1% (AHI ≥ 15). Multiple stepwise logistic regression analysis identified BMI, habitual snoring, time taken to fall asleep, and age as predictors of SDB at AHI ≥ 5. Analysis of anthropometric parameters indicated that the relative risk of OSAS attributable to obesity was less than in white subjects.

Conclusion: This community-based study of sleep apnea among middle-aged men in Hong Kong using full PSG demonstrated an estimated prevalence of OSAS (AHI ≥ 5 and EDS) at 4.1%. Increasing BMI and age were associated with SDB, although factors other than adiposity may also have an important pathogenic role in OSA in Chinese subjects.

Figures in this Article

Sleep-disordered breathing (SDB) is now recognized to be an important health issue in western countries,12 due to its high prevalence36 and the growing evidence of its significant association with morbidity and, possibly, mortality.711 There have been many epidemiologic studies that aim to establish the prevalence of SDB and obstructive sleep apnea syndrome (OSAS) in various populations. Previous studies from the United States, United Kingdom, and Australia have reported prevalence rates of SDB in middle-aged men to be in the range of 5 to 26%, using different diagnostic methods and criteria,36 and that of symptomatic sleep apnea in the range of 3 to 4%.34,6 Major etiologic factors, such as obesity34,12 and craniofacial anatomic predisposition,1214 are both genetically and environmentally influenced, and it is therefore pertinent to determine the prevalence of sleep apnea in different populations.

To date, there has been scanty documentation of the prevalence of SDB in Asians. Reported data were based on symptoms,15 portable sleep monitoring systems,1617 or cohorts of subjects with specific medical problems.1819 The main objective of this study was to obtain an estimate of the prevalence of SDB documented with polysomnography (PSG) in middle-aged Chinese men, using a cohort of male office-based workers in Hong Kong as a model. The secondary objective was to determine the clinical and anthropometric features that were predictive of SDB in this cohort.

This study was performed in Hong Kong. Data were collected between July 1997 and April 1999.

Sample

The target population included male office-based workers in three public institutions in Hong Kong. We distributed a questionnaire (modified from NAPS Document No. 05017)3 to men aged 30 to 60 years, to be filled out by the subjects. It consisted of questions concerning demographic data, sleep habits, snoring history, breathing irregularities and leg movements during sleep, daytime sleepiness, smoking and drinking history, medical history, family history of sleep apnea, and job nature. All subjects were invited at the same setting to undergo sleep study, and those who volunteered were contacted for subsequent PSG. The study was approved by the Ethics Committee of The University of Hong Kong.

Collection of PSG Data

Studies were conducted at the sleep laboratory at Queen Mary Hospital. Measures of body habitus were recorded by standard anthropometric methods.20 BP was checked in the morning after PSG. PSG (Alice 3 System; Healthdyne; Atlanta, GA) consisted of continuous polygraphic recording from surface leads for EEG, electro-oculography, electromyography, ECG, thermistors for nasal and oral airflow, thoracic and abdominal impedance belts for respiratory effort, pulse oximetry for oxyhemoglobin level, tracheal microphone for snoring, and sensors for leg and sleep position.

Interpretation of PSG Data

PSG records were scored manually. Sleep data were scored according to standard criteria.21An abnormal breathing event during objectively measured sleep was defined according to the commonly used clinical criteria of either a complete cessation of airflow lasting ≥ 10 s (apnea) or a discernible reduction in airflow accompanied by a decrease of ≥ 4% in oxyhemoglobin saturation (hypopnea). The average number of episodes of apnea and hypopnea per hour of sleep (the apnea-hypopnea index [AHI]) was calculated as the summary measurement of SDB. Arousals were identified according to established criteria.22

Assessment of Daytime Sleepiness

Daytime sleepiness was assessed with four subjective questions. Using a 5-point scale (0 to 4), the subjects rated how often they (1) felt excessively sleepy during the daytime; (2) felt unrefreshed or tired during the day, regardless of how long they had slept; (3) fell asleep or dozed off momentarily while watching TV, reading, or at meetings/church; and (4) felt sleepy while driving. The answer was considered positive if the score was ≥ 2. Subjects were identified as having excessive daytime sleepiness (EDS) if they gave a positive response to three of the four questions.

Definition of SDB and OSAS

The minimum criterion for SDB was AHI ≥ 5, and data for three AHI cutoff threshold values at 5, 10, and 15, respectively, are presented. Similarly, the minimum criterion for diagnosis of OSAS was AHI ≥ 5 in the presence of EDS (as defined by the questions above), and data for three cutoff AHI values are presented .

Clinical Assessment of Subjects

All subjects who had an AHI ≥ 5 on PSG (n = 64) were recalled for assessment. In particular, symptoms of OSAS and other vascular risks were reassessed. Subjects were given management advice along the usual code of practice in our medical center, which was adapted from current opinion.2324

Calculation of Prevalence

Questionnaire respondents were classified into two groups based on the self-reported presence of snoring: group 1, habitual snorers (snoring frequency ≥ 3 days per week; group 2, nonhabitual snorers (snoring frequency < 3 days per week). Those who were not sure were classified as nonhabitual snorers.

About 20% of the questionnaire respondents had PSG performed, and the PSG subjects were considered sample subjects for their corresponding groups (snorers or nonsnorers) who only responded to questionnaire. The mean age and body mass index (BMI) of sample subjects were compared with those who did not have PSG in the respective snoring category. If no significant difference was found, the prevalence rate of SDB in the PSG group of snorers or nonsnorers would be considered representative of the corresponding questionnaire respondents group.25 If a significant difference was found between the PSG group and no-PSG group, a conservative estimate was adopted, treating the SDB subjects documented by PSG as the only subjects with SDB in the entire corresponding questionnaire group. The overall prevalence of SDB in the entire cohort would be calculated as follows: the estimated number of subjects with SDB among snorers and nonsnorers/total number of questionnaire respondents × 100%.

Age-adjusted and BMI-adjusted prevalence rates were calculated by categorizing subjects into three age groups (30 to 39 years, 40 to 49 years, and 50 to 60 years) and whether their BMI was < 23 or ≥ 23, where 23 is the recently proposed threshold BMI value for overweight in Asians.26

Statistical Analysis

Descriptive statistics were used to summarize subject characteristics and questionnaire data. Comparison between groups was done with the Student’s t test for continuous variables and Pearson’s χ2 test for discrete variables. All significance tests were two sided, and a value of p < 0.05 was considered statistically significant. To adjust the effect of various factors on the likelihood of developing snoring and SDB, a multiple logistic regression analysis was employed. This analysis included all variables that were found to be significant in the respective between-group comparisons (Table 1). Stepwise logistic regression was used to determine the principal covariates affecting SDB.

The association of SDB with obesity, reflected by body habitus parameters, was further examined by multiple logistic regression. A separate model was fitted for each measure of body habitus because of multicollinearity. Age was included in all the models. All analysis was done with statistical software (Statistical Package for Social Science, release 10.0 for Windows; SPSS; Chicago, IL).

Questionnaire Data

Questionnaires were distributed to 1,542 men and returned by 784 (51%). Seven hundred seventy-three completed questionnaires were analyzed, while another four subjects responded that they already had a diagnosis of obstructive sleep apnea and were receiving nasal continuous positive airway pressure (nCPAP) treatment. Age and BMI of questionnaire respondents who did not come for PSG were based on self-reporting, while those of the PSG group were available from both self-reporting and measurement at PSG. In the latter group, the mean age was the same on both occasions, while the mean of self-reported BMI was lower than measured values by 2%.

The questionnaire respondents had a mean age of 41 years and mean BMI of 23.9, which were similar to those of the general community for the target age group (30 to 60 years) and gender (men) at approximately 42 years of age and 24 BMI, respectively.2729 The percentage of self-reported habitual snorers was 23%, and the mean age, BMI, and features suggestive of sleep apnea were significantly higher among habitual snorers (Table 1). Both snorers and nonsnorers showed significant difference in BMI (p < 0.001) between subjects who came for PSG and those who did not. Stepwise logistic regression identified EDS, history of hypertension, witnessed breathing abnormality, BMI, and leg movements during sleep as significant correlates of habitual snoring.

PSG Data

One hundred fifty-three questionnaire respondents came for PSG. Among those who did not come, 90 respondents were contacted by telephone; the reasons given for refusal were the inconvenience of the test, and their subjective assessment that they had no sleep problem. Of 153 polysomnograms, 3 were rejected: 2 due to suboptimal technical recording and 1 due to insufficient sleep time (< 4 h). The distributions of sleep stages of the PSG-positive group (AHI ≥ 5) and PSG-negative group were similar, but those with AHI ≥ 5 spent more time sleeping on their backs, had more snoring, and had higher arousal indexes (Table 2).

Prevalence of SDB and OSAS

Among the 150 patients who underwent PSG, 64 subjects (43%), 45 subjects (31%), and 37 subjects (25%) had AHIs ≥ 5, ≥ 10, and≥ 15, respectively. Since in both snorers and nonsnorers the PSG subjects had significantly higher BMIs than the corresponding no-PSG subjects, the projection of the prevalence of SDB was based on the conservative estimate (ie, assuming that no subject in the no-PSG group would have SDB). Including the four subjects with OSAS already diagnosed, the minimum prevalence of SDB (AHI ≥ 5) and OSAS (AHI ≥ 5 and EDS) in the original study population of 1,542 men would be 4.4% and 2.1%, respectively. Based on the observation that the age and BMI of the questionnaire respondents were similar to those of the general male population in the corresponding age strata in Hong Kong, it would be acceptable to use the questionnaire respondents as the denominator of evaluation. This would yield an estimated prevalence of SDB and OSAS using various cutoff points of AHI, respectively, at 8.8% and 4.1% (AHI ≥ 5), 6.3% and 3.2% (AHI > 10), and 5.3% and 3.1% (AHI > 15; Fig 1).

Factors Associated With SDB

The significant correlates of SDB in the PSG subjects are shown in Table 3. Age and BMI both correlated with AHI but not EDS. Stepwise linear logistic regression selected and retained BMI, habitual snoring, time taken to fall asleep at night, and age as the principal covariates.

Figure 2 shows the age-specific prevalence of SDB and OSAS in the target population, and the results in Table 4 suggest an increasing trend for SDB with age, which was also present in both groups of subjects with BMI < 23 and BMI ≥ 23.

Table 5 shows the odd ratios estimating the increased risk of SDB in PSG subjects associated with an increment of 1 SD in the value of the specific measure of body habitus.

Validity of Self-Reported Snoring

Among the 150 subjects who underwent PSG, 11 subjects who denied any snoring (ie, never snorers) snored on PSG night. Seven of these subjects snored for < 10% of the night, and all snored for< 50% of the night. Of the 139 patients who admitted to snoring, 6 patients showed no evidence of snoring (all 6 reported snoring only rarely) and 45 patients snored < 10% of the night.

Clinical Reassessment of the Group With AHI ≥ 5

Sixty of the 64 subjects with SDB returned on recall. Four subjects (all with AHI < 15) claimed no symptoms and turned down the appointment. Of the 64 subjects, 28 subjects were initially considered to have symptomatic SDB from questionnaire data. At clinical reassessment, two subjects denied significant daytime sleepiness (one of them had significant weight reduction), while the remaining 26 subjects were symptomatic and were offered nCPAP. Of these, 7 subjects declined any treatment, 18 subjects received nCPAP, and all reported significant symptomatic improvement, while 1 subject received oral appliance with modest improvement. The other asymptomatic subjects all opted for weight reduction, except two subjects who had vascular risk factors (hypertension and diabetes mellitus) and received nCPAP and oral appliance, respectively.

In this community-based study of the prevalence of SDB using full PSG, we estimate that about 9% of this cohort of middle-aged male office workers had SDB at AHI ≥ 5, and 4.1% were symptomatic with daytime sleepiness.

Limitations of Study

An ideal study of prevalence involves assessment of each subject in a large population with a “gold standard” diagnostic test (ie, overnight PSG in this context). However, this is extremely difficult in the assessment of SDB because the diagnostic test is time consuming for the subject and expensive for the investigator. Most studies have therefore elected to study a portion of the population of interest and then estimate the prevalence of the entire population, using either a combination of questionnaire and a full/portable diagnostic system, or even questionnaires only. There is a potential for bias when patients are sampled from a large population and the results extrapolated back to the total group. In the present study, only half of the questionnaires were returned. However, the questionnaire respondents had mean age and BMI that were similar to those of men in the target age strata in the local community; hence, we believe that they were a nonbiased sample in terms of risks for SDB. The limited participation rate for PSG was expected due to substantial participant burden. Since the subjects came on a voluntary basis, self-selection bias may be present and indeed some features associated with sleep apnea were more prevalent in those who came for study. Hence, we adopted the conservative estimate, assuming that all those who did not undergo PSG did not have SDB, which may potentially underestimate the prevalence of SDB.

Only a single-night study was done, and some mild cases might have been missed due to night-to-night variation; therefore, the true prevalence of SDB would be underestimated. However, several studies had shown that the mean AHI between the initial and second laboratory studies did not differ significantly.3,3031

Our assessment of EDS was based on four questions relating to sleepiness. Although the sleepiness score thus obtained has not been validated against objective tests of sleepiness in this study, the questions were adapted from those validated in other studies.3,32 Furthermore, the four questions used in this study have been validated regarding their internal consistency, and the score thus derived correlated well with the Epworth Sleepiness Scale score,32 which was also assessed in the 150 subjects who came for PSG, as well as in another 120 subjects referred to our sleep clinic for clinical evaluation (data not shown).

Strengths of the Study

We used recommended in-laboratory full PSG for documentation of SDB. We studied healthy office workers who were similar to the local male population in two parameters that are important determinants of SDB, BMI, and age; therefore, the results of the study may be applicable to other men in the target age range.

Different from other population studies of SDB, all subjects with documented SDB have been recalled for clinical evaluation by a respiratory physician. This would allow confirmation of those subjects who suffer from clinically important SDB.

Prevalence of Snoring, SDB, and OSAS

The estimated prevalence of SDB (AHI ≥ 5) at 8.8% in Chinese men from 30 to 60 years old is much lower than that of studies in white subjects utilizing similar diagnostic criteria,34 which reported a prevalence of about 25%. Our results are nearer to those of a study of Chinese subjects in Singapore utilizing a diagnostic triad of self-reported snoring, sleep symptoms of apnea/hypopnea, and/or hypertension/wide neck circumference, which arrived at an estimated SDB prevalence of 5.8% in the age range of 40 to 59 years.15 This would suggest that the prevalence of SDB in Chinese subjects is really lower than that in white subjects. Despite this difference in the prevalence of SDB, the estimated prevalence of symptomatic SDB in our community at about 4% is very comparable to that reported in white populations. It is unlikely that the estimation of OSAS was factitiously high, since we have reassessed the majority of subjects with SDB and fully evaluated their symptoms again. One possible reason for this difference in the prevalence of SDB, compared to white series, may be self-selection bias that favored recruitment of PSG subjects with EDS, the main distinguishing criterion between SDB and OSAS. This would lead to most of the OSAS subjects being identified and only a minority of SDB subjects being identified, since those without symptoms have not undergone PSG. The prevalence of OSAS we found is much higher then that recently reported,17 at 0.1 to 2.3% in Chinese male and female students aged 19 years based on limited PSG (MESAM IV; Madaus Medicin-Elektronik; Freiburg, Germany) in a random sample of 88 of 1,901 questionnaire respondents. It is recognized that the prevalence of sleep apnea is higher in middle-aged subjects and higher in men then women; therefore, the substantial difference in prevalence of OSAS reported from the two studies is not unexpected

Correlates of SDB

Obesity is a significant risk factor for SDB in white populations.36 In this study, a higher BMI was a risk factor for SDB in Chinese subjects as well. Obesity defined33 as BMI > 30 is not a common problem in Chinese subjects, as evidenced by only 5% of the study subjects having BMI> 30. However, recently, a new consensus for definition of obesity in Asians has been proposed, with BMI ≥ 23 as the threshold at risk value for obesity.26 The mean BMI of the present cohort at 24 is similar to that reported by other studies of random community male subjects in the same age strata in Hong Kong.2829 This BMI value is lower than that reported in white communities,4,25,33 but more comparable to that of other Chinese ethnic populations.15 Therefore, our subjects with SDB whose mean BMI was 27 were obese by peer comparison. To further assess the impact of obesity on SDB in our population, the relative risks of having SDB in relation to measures of body habitus were calculated. On comparing the odds ratios in our subjects with those reported in the Wisconsin study,3 the risks of having SDB due to an increase in any index of adiposity were much lower in our population. Since the prevalence of OSAS in Chinese subjects is comparable to that of white subjects, these findings suggest that adiposity, although a definite risk factor for SDB in Chinese subjects, carries less weight than it did in white subjects (Table 5). The other risk factors for SDB, such as pharyngeal narrowing, retrognathia or micrognathia, and pharyngeal collapsibility might assume greater pathogenic significance in Chinese subjects.

The correlation between age and SDB has been studied by different investigators with dissimilar results, with suggestion of a rise in prevalence of SDB with age.34 We found a rising trend in the prevalence of SDB as age increased, which was evident in both BMI < 23 and ≥ 23 groups (Table 4).

Although SDB is a relatively common problem, there is currently no reliable screening test for the disorder. In this cohort, EDS did not correlate with SDB. Since sleepiness, regardless of the cause, probably favored self-selection for PSG, its discriminating power within this cohort would be diminished. As indicated by logistic regression analysis, parameters including higher BMI, habitual snoring, ease of falling asleep at night, and older age were predictive of the presence of SDB. The application of these easily identifiable predictive factors would assist in appropriate referral and prioritization for PSG. With the high prevalence of SDB and limited resources, this might be useful for better utilization of resources.

To the best of our knowledge, this is the first report of the prevalence of OSAS in middle-aged Chinese men using full overnight PSG. The study demonstrated that symptomatic OSAS affected about 4% of middle-aged male office-workers. An increase in BMI was an important predictor of SDB, although compared to white subjects the mean BMI of Chinese subjects with SDB was lower and the relative risks of developing SDB conferred by various indexes of obesity were also less. Other risk factors (in particular, local anatomic features) that predispose to SDB in Chinese populations warrant further study.

Abbreviations: AHI = apnea-hypopnea index; BMI = body mass index; EDS = excessive daytime sleepiness; nCPAP = nasal continuous positive airway pressure; OSAS = obstructive sleep apnea syndrome; PSG = polysomnography; SDB = sleep-disordered breathing

This study was supported by the Competitive Earmarked Research Grant HKU457/96M from the Hong Kong Research Grants Council, Hong Kong.

Figure Jump LinkFigure 1. Prevalence rates of SDB in 777 questionnaire respondents using various cutoff points for AHI.Grahic Jump Location
Figure Jump LinkFigure 2. Age-specific prevalence rates of SDB (AHI ≥ 5) and OSAS in 777 questionnaire respondents.Grahic Jump Location
Table Graphic Jump Location
Table 1. Features Showing Significant Difference Between Snorers and Nonsnorers*
* 

Data are presented as mean ± SD or No. (%) unless otherwise indicated.

 

Comparison between habitual snorers and nonhabitual snorers, p < 0.05.

 

Comparison between habitual and nonhabitual snorers, p < 0.001.

Table Graphic Jump Location
Table 2. PSG Data*
* 

Data are presented as mean ± SD unless otherwise indicated. NS = not significant.

Table Graphic Jump Location
Table 3. Correlates of SDB Based on Demographic, Anthropometric, Questionnaire, and PSG Data*
* 

Data are presented as absolute values or No. (%) unless otherwise indicated. See Table 2 for abbreviation.

Table Graphic Jump Location
Table 4. Prevalence of SDB in Different Age Groups With Correction for BMI*
* 

CI = confidence interval.

Table Graphic Jump Location
Table 5. Relative Risks for SDB and Measures of Body Habitus*
* 

See Table 4 for abbreviation.

The authors thank Ms. Audrey Ip and Mr. K. M. Lo for technical assistance and Professor M. Chan for clinical contribution. We also gratefully acknowledge the institutions that have allowed us to conduct the study among their employees, and the people who participated in the study.

Phillipson, EA (1993) Sleep apnea: a major public health problem.N Engl J Med328,1271-1273. [CrossRef] [PubMed]
 
Strohl, KP, Redline, S Recognition of obstructive sleep apnea.Am J Respir Crit Care Med1996;154,279-289. [PubMed]
 
Young, T, Palta, M, Dempsey, J, et al The occurrence of sleep-disordered breathing among middle-aged adults.N Engl J Med1993;328,1230-1235. [CrossRef] [PubMed]
 
Bearpark, H, Elliott, L, Grunstein, R, et al Snoring and sleep apnea: a population study in Australian men.Am J Respir Crit Care Med1995;151,1459-1465. [PubMed]
 
Olson, LG, King, MT, Hensley, MJ, et al A community study of snoring and sleep-disordered breathing: prevalence.Am J Respir Crit Care Med1995;152,711-716. [PubMed]
 
Ohayon, M, Guillemenault, C, Priest, RG, et al Snoring and breathing pauses during sleep: telephone interview survey of a United Kingdom population sample.BMJ1997;314,860-863. [CrossRef] [PubMed]
 
Ferguson, KA, Fleetham, JA Sleep-related breathing disorders: 4. Consequences of sleep disordered breathing.Thorax1995;50,998-1004. [CrossRef] [PubMed]
 
Hla, KM, Young, TB, Bidwell, T, et al Sleep apnea and hypertension: a population based study.Ann Intern Med1994;120,382-388. [PubMed]
 
Teran-Santos, J, Jimenez-Gomez, A, Cordero-Guevara, J, et al The association between sleep apnea and the risk of traffic accidents.N Engl J Med1999;340,847-851. [CrossRef] [PubMed]
 
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Figures

Figure Jump LinkFigure 1. Prevalence rates of SDB in 777 questionnaire respondents using various cutoff points for AHI.Grahic Jump Location
Figure Jump LinkFigure 2. Age-specific prevalence rates of SDB (AHI ≥ 5) and OSAS in 777 questionnaire respondents.Grahic Jump Location

Tables

Table Graphic Jump Location
Table 1. Features Showing Significant Difference Between Snorers and Nonsnorers*
* 

Data are presented as mean ± SD or No. (%) unless otherwise indicated.

 

Comparison between habitual snorers and nonhabitual snorers, p < 0.05.

 

Comparison between habitual and nonhabitual snorers, p < 0.001.

Table Graphic Jump Location
Table 2. PSG Data*
* 

Data are presented as mean ± SD unless otherwise indicated. NS = not significant.

Table Graphic Jump Location
Table 3. Correlates of SDB Based on Demographic, Anthropometric, Questionnaire, and PSG Data*
* 

Data are presented as absolute values or No. (%) unless otherwise indicated. See Table 2 for abbreviation.

Table Graphic Jump Location
Table 4. Prevalence of SDB in Different Age Groups With Correction for BMI*
* 

CI = confidence interval.

Table Graphic Jump Location
Table 5. Relative Risks for SDB and Measures of Body Habitus*
* 

See Table 4 for abbreviation.

References

Phillipson, EA (1993) Sleep apnea: a major public health problem.N Engl J Med328,1271-1273. [CrossRef] [PubMed]
 
Strohl, KP, Redline, S Recognition of obstructive sleep apnea.Am J Respir Crit Care Med1996;154,279-289. [PubMed]
 
Young, T, Palta, M, Dempsey, J, et al The occurrence of sleep-disordered breathing among middle-aged adults.N Engl J Med1993;328,1230-1235. [CrossRef] [PubMed]
 
Bearpark, H, Elliott, L, Grunstein, R, et al Snoring and sleep apnea: a population study in Australian men.Am J Respir Crit Care Med1995;151,1459-1465. [PubMed]
 
Olson, LG, King, MT, Hensley, MJ, et al A community study of snoring and sleep-disordered breathing: prevalence.Am J Respir Crit Care Med1995;152,711-716. [PubMed]
 
Ohayon, M, Guillemenault, C, Priest, RG, et al Snoring and breathing pauses during sleep: telephone interview survey of a United Kingdom population sample.BMJ1997;314,860-863. [CrossRef] [PubMed]
 
Ferguson, KA, Fleetham, JA Sleep-related breathing disorders: 4. Consequences of sleep disordered breathing.Thorax1995;50,998-1004. [CrossRef] [PubMed]
 
Hla, KM, Young, TB, Bidwell, T, et al Sleep apnea and hypertension: a population based study.Ann Intern Med1994;120,382-388. [PubMed]
 
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