Prevalence of Symptoms and Risk of Sleep Apnea in the US Population* Results From the National Sleep Foundation Sleep in America 2005 Poll

Original Research SLEEP MEDICINE Prevalence of Symptoms and Risk of Sleep Apnea in the US Population* Results From the National Sleep Foundation Sleep in America 2005 Poll David M. Hiestand, MD, PhD; Pat Britz, MEd, MPM; Molly Goldman, BA; and Barbara Phillips, MD, MSPH, FCCP Background: Obstructive sleep apnea (OSA) is a common medical condition with significant adverse consequences, but OSA remains undiagnosed in many individuals. The Berlin questionnaire is a validated instrument that is used to identify individuals who are at risk for OSA. Design: We conducted an analysis of data from the Sleep in America 2005 Poll of The National Sleep Foundation (NSF). The NSF poll is an annual telephone interview of a representative sample of US adults. Participants: The 2005 NSF poll included 1,506 adults. The mean age of participants was 49 years (775 were women). Measurements: The Berlin questionnaire was embedded in the NSF poll. This instrument includes questions about snoring, witnessed apneas, self-reported hypertension, and daytime sleepiness. Height and weight were included for the calculation of body mass index (BMI). The NSF poll included detailed demographic information and extensive questions related to all aspects of sleep. Results: Of the 1,506 respondents, 26% (31% of men and 21% of women) met the Berlin questionnaire criteria indicating a high risk of OSA. The risk of OSA increased up to age 65 years. A significant number of obese individuals (57%) were at high risk for OSA. Those whose Berlin questionnaire scores indicated a high risk for OSA were more likely to report subjective sleep problems, a negative impact of sleep on quality of life, and a chronic medical condition than those who were at lower risk. Conclusions: As many as one in four American adults could benefit from evaluation for OSA. Considering the serious adverse health and quality-of-life consequences of OSA, efforts to expedite diagnosis and treatment are indicated. (CHEST 2006; 130:780 786) Key words: epidemiology; obesity; obstructive sleep apnea; poll; public health; sleep hygiene; sleepiness Abbreviations: AHI apnea-hypopnea index; BMI body mass index; CI confidence interval; NSF National Sleep Foundation; OSA obstructive sleep apnea; RDI respiratory disturbance index; RR relative risk Obstructive sleep apnea (OSA) is a common medical condition with serious adverse consequences. The most significant medical consequences include increased risk of hypertension, 1,2 coronary *From the Division of Pulmonary, Critical Care, and Sleep Medicine (Drs. Hiestand and Phillips), University of Kentucky College of Medicine, Lexington, KY; the National Sleep Foundation (Ms. Britz), Washington, DC; and WB&A Market Research (Ms. Goldman), Annapolis, MD. The authors have reported to the ACCP that no significant conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article. Manuscript received November 21, 2005; revision accepted March 7, 2006. vascular disease, 3 congestive heart failure, 4 cerebrovascular disease, 5 glucose intolerance, 6 and impotence. 7 Severe, untreated OSA has recently been linked to increased cardiovascular mortality. 8 10 In addition to its contribution to medical disease, un- Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal. org/misc/reprints.shtml). Correspondence to: David M. Hiestand, MD, PhD, K528 Kentucky Clinic, Division of Pulmonary, Critical Care, and Sleep Medicine, 740 South Limestone St, Lexington, KY 40536-0028; e-mail: Dmhies00@email.uky.edu DOI: 10.1378/chest.130.3.780 780 Original Research

treated OSA can cause daytime somnolence, cognitive impairment, loss in work productivity, and increased risk of automobile crashes. 11 13 The prevalence of OSA in the United States is currently estimated to be between 5% and 10%. 14,15 It is estimated that only 10% of the population has been adequately screened for appropriate diagnosis. 16 This estimate is based on the prevalence of risk factors for OSA in the population. The at-risk population, however, is much larger, and the means to appropriately screen patients remains to be accurately defined. One screening tool is the Berlin questionnaire, which is a simple instrument that has been studied in primary care settings. 17,18 This instrument is used to classify subjects who are at high risk and low risk for OSA by identifying snoring behavior, daytime sleepiness, obesity, and hypertension. This tool has reasonable sensitivity, specificity, and positive predictive value in a primary care population. For example, in a study of 744 adult respondents, 37.5% were identified as being at high risk by the application of the Berlin questionnaire. 17 A subset of 100 of these 744 respondents underwent portable polysomnography, and were identified as being at high risk when the results of the Berlin questionnaire predicted a respiratory disturbance index (RDI) of 5 with a sensitivity of 0.86, a specificity of 0.77, a positive predictive value of 0.89, and a likelihood ratio of 3.79. In a study of 8,000 primary care patients from the United States and Europe, 32% had a high pretest probability for OSA 19 based on the Berlin questionnaire. The purpose of this analysis was to assess the prevalence of individuals who were at risk for OSA in a broad sample of the US population, using the Berlin questionnaire. We further characterized the population at high risk for OSA in terms of their responses to general questions about sleep and self-reported concomitant medical conditions. Materials and Methods Data pertaining to the prevalence of those at risk for sleep apnea in this report are from the 2005 National Sleep Foundation (NSF) annual Sleep in America poll. The NSF is an independent nonprofit organization that is dedicated to improving public health and safety by achieving an understanding of sleep and sleep disorders, and by supporting education, sleep-related research, and advocacy (www.sleepfoundation.org). Established in 1990, the NSF relies on voluntary contributions as well as grants from foundations, corporations, government agencies, and other organizations to support its programs. The NSF conducts Sleep in America polls annually, with the release of the results timed to coincide with National Sleep Awareness Week, which is the week before the change to Daylight Savings Time in the spring. The topics and questions included in the poll are selected by a subset of volunteers, staff, and board members, and there is no commercial or industry influence on this poll. Some topics and questions are maintained from year to year in order to assess trends over time. The 2005 poll included questions regarding sleep and sleep habits. Since the diagnosis of OSA can be suspected with a high degree of likelihood on the basis of history and anthropometric data, 20 23 we deemed it possible and appropriate to learn about the prevalence and risks of this cluster of symptoms in a survey of sleep habits. The instrument included to evaluate risk of OSA was the Berlin questionnaire. The Berlin questionnaire was developed in 1996. It has been previously validated in a community survey, which was used in conjunction with portable monitoring. 18 In that study, the questionnaire was found to predict an RDI of 5 with a sensitivity of 0.86, a specificity of 0.77, a positive predictive value of 0.89, and a likelihood ratio of 3.79. The content of the Berlin questionnaire has been previously described in detail. 17 Briefly, the questionnaire is divided into three sections. In section 1, respondents are asked whether they snore. Those who respond affirmatively are asked how loud the snoring is, how often it occurs, and whether their snoring bothers other people. Respondents are also asked whether anyone has ever noticed the cessation of breathing during sleep. In section 2, respondents are asked how often they feel tired or fatigued after sleep, how often they feel tired, fatigued, or not up to par during wake time, and whether they ever fall asleep driving a car. In section 3, respondents are asked about a personal history of hypertension, as well as their height, weight, age, and sex. Body mass index (BMI) is calculated from the information in section 3. A section is considered positive if there are two affirmative answers in either section 1 or 2, or one affirmative response in section 3. Individuals who have positive scores in two of the three sections are considered to be at risk for OSA. The version of the Berlin questionnaire that was used in this study is included in the Appendix. In the 2005 NSF poll, a variety of other information about sleep, sleep habits, lifestyle, and illnesses were collected. Individuals were also asked whether they felt they had a sleep problem. For the purposes of the poll, symptoms of sleep problems were defined as follows: (1) having difficulty falling asleep; (2) waking a lot during the night; (3) waking up too early and not being able to get back to sleep; (4) waking up feeling unrefreshed; (5) snoring; (6) unpleasant feelings in the legs; or (7) experiencing pauses in breathing. Respondents were also asked whether they had ever been told by a doctor that they had the following medical conditions (yes, no): heart disease; high BP; arthritis; diabetes; lung disease; heartburn or gastroesophageal reflux disease; anxiety disorder; or depression. A random sample of telephone numbers was purchased, and quotas were established by region and age, based on household data from the US Census. The total sample size was designed to be 1,500 participants. Telephone interviews were conducted between September 20 and November 7, 2004, resulting in a random sample of 1,506 adults. The interviews averaged 20 min in duration. In order to qualify for inclusion in the survey, participants had to be community-dwelling (eg, not residing in institutions), 18 years of age, and living within the continental United States. Interviewers explained the poll to participants by reading a script that said, I am calling on behalf of the NSF to conduct a survey about sleep among Americans. This is not a sales call; it is a national research survey. It will take a few minutes of your time and your responses will be kept strictly confidential. A total of 26,847 households were called; 4,343 did not answer repeated phone calls, and 4,168 potential participants refused to participate. Thus, the participation rate calculated by taking the number of completed interviews divided by the number of completed interviews plus the number of contacted households who refused participation or did not qualify was 23%. Response www.chestjournal.org CHEST / 130 / 3/ SEPTEMBER, 2006 781

rates did not vary by region of the country. Institutional review board approval is not required to conduct or publish the results of a poll without any individual identifying information that is conducted by a nonprofit independent organization. There was no compensation for participation. Approximately 80% of the interviewing was conducted on weekdays between 5:00 pm and 8:00 pm, on Saturdays between 10:00 am and 4:00 pm, and on Sundays between 4:00 pm and 8:00 pm by professional interviewers from WB&A Market Research (Annapolis, MD) on behalf of the NSF. Results The characteristics of the sample are listed in Table 1. This sample included a similar number of men (n 731; 49%) and women (n 775; 51%). The mean age was 49 years. Most reported having a partner, with 62% married, 33% single, and 5% living with someone ( partnered ). Geographic distribution was consistent with the US population, as follows: 36% lived in the South; 21% lived in the West; 24% lived in the Midwest; and 19% lived in the Northeast. The race/ethnicity of the sample included 84% who described themselves as white/ white and 16% who described themselves as minority/other. A majority (52%) were employed full-time, and, of those, 80% worked regular day shifts. The total poll sample represented the US population in terms of BMI and chronic medical conditions (Table 1). Of the 1,506 respondents, 895 (59%) reported snoring. Of those who snored, 54% did so 3 nights per week, and 40% did so every night or almost every night. Most snorers reported that their Table 1 Demographic and Anthropometric Characteristics of the 2005 Sleep in America Poll Respondents (n 1,506) Variables No. (%) Age Average 49 yr 18 29 yr 177 (12) 30 49 yr 616 (41) 50 64 yr 426 (29) 65 yr 273 (18) Men 775 (49) Women 731 (51) White 1284 (85) Minority/other 222 (15) Weight Underweight 45 (3) Normal (ie, BMI 25) 477 (33) Overweight (ie, BMI 25 30) 556 (38) Obese (ie, BMI 30) 379 (25) Medical conditions Hypertension 440 (29) Diabetes 164 (11) Heart disease 140 (10) Tobacco use 379 (25) snoring has bothered others. Witnessed pauses in breathing were strikingly common, with 96 respondents (6%) reporting witnessed pauses on 3 nights per week. The presence of witnessed pauses was found almost exclusively in those individuals who were found to have a high risk according to the Berlin questionnaire score (88 of 96 respondents; 92%), but it was found in only 23% of persons in this group. Sleepiness symptoms were common in the population. A total of 387 persons (26%) reported waking feeling tired or fatigued on 3 days of the week. This symptom was much more common in the high-risk group determined by the Berlin questionnaire results, having been reported by 244 persons (63%) in this group. Nearly a fifth of all respondents (272; 18%) reported being late to work due to a sleep problem. This finding was slightly more common in those with a high-risk Berlin questionnaire score (25% vs 16% of those with low risk). Alarmingly, 478 respondents (32%) reported driving drowsy one or more times per month. This finding was more common in those with a high-risk Berlin questionnaire score (48% vs 26%, respectively). The risk of OSA as determined by Berlin questionnaire score increased linearly with increasing age, as shown in Figure 1. Nineteen percent of those persons 18 to 29 years of age were at high risk as were 25% of those 30 to 49 years of age, and 33% of those 50 to 64 years of age. The risk declined after the age of 65 years, with 21% of persons in this older group defined as being at high risk. In the group of persons 18 to 29 years of age, high risk was equally distributed between men and women. In all other age groups, however, more men than women were identified as being at high risk based on Berlin questionnaire score. Overall, 31% of men were in the high-risk group compared to 21% of women (p 0.001). Snoring ( 3 nights per week) was also more common in men, occurring in 19% vs 13% of women (p 0.001). Similarly, witnessed apneas ( 3 nights per week) were reported by 4% of men vs 2% of women (p 0.01). Obesity strongly predicted the Berlin questionnaire score (Fig 2). Among obese individuals (ie, BMI 30 kg/m 2 ), 59% had a high-risk Berlin questionnaire score. Those individuals with a low BMI (ie, 20 kg/m 2 ) had a negligible relative risk (RR) of a high-risk score at 0.2% (95% confidence interval [CI], 0.03 to 1.50%). The RR increased with BMI class, with those with a BMI of 25 to 30 kg/m 2 having an RR of 1.63 (95% CI, 1.18 to 2.24), those with a BMI of 30.1 to 40 kg/m 2 having an RR of 5.38 (95% CI, 4.08 to 7.12), and those with a BMI of 40 kg/m 2 having an RR of 7.11 (95% CI, 5.25 to 9.64). 782 Original Research

Figure 1. Prevalence of positive Berlin questionnaire scores by age for men and women. The presence of any chronic medical condition was also associated with a high-risk Berlin questionnaire score. Overall, those persons reporting a chronic medical illness (identified above) were more likely to have a high-risk Berlin questionnaire score (35% vs 11% of those with a low-risk score). Discussion The most striking finding of this study was that one in four individuals of a representative sample of US adults appears to be at high risk for OSA. In 1993, the classic Wisconsin Sleep Cohort Study reported Figure 2. Prevalence of positive Berlin questionnaire scores by BMI. that 4% of men and 2% of women cohort met what the investigators called minimal diagnostic criteria for OSA, defined as an apnea-hypopnea index (AHI) of 5 events per hour that was associated with daytime hypersomnolence. 24 This value appears repeatedly in the current literature. In this same cohort, however, 9% of women and 24% of men had an AHI of 5 events per hour, and 44% of men and 28% of women were habitual snorers. Subsequent to this widely quoted study, the US population has aged and become more obese. The risk of significant sleep-disordered breathing rises both with BMI 25 and with age. 15 In addition to the fact that the risk factors for sleep apnea are increasing in the general population, the diagnostic criteria for sleep apnea continue to evolve, which results in a shifting metric, making prevalence hard to estimate. In an exhaustive review of currently available data, Young and colleagues 15 revisited the prevalence of sleep apnea, and estimated that 5% of adults in Western countries have sleep apnea syndrome with sleepiness and an unknown fraction have sleep-disordered breathing without overt sleepiness. However, even that estimate is probably an underestimate. For example, the Sleep Heart Health Study 26 reported that 22% of 1,824 people had an RDI of 15 events per hour, which most practitioners would consider to be significant sleep apnea. This cohort had a mean age of 65 years, and a mean RDI of 10.9 events per hour of sleep. In a study of sleep apnea incidence, the Cleveland Family Study 14 of 285 individuals without significant sleep apnea at www.chestjournal.org CHEST / 130 / 3/ SEPTEMBER, 2006 783

baseline demonstrated that the incidence of the development of sleep-disordered breathing (AHI, 5 events per hour) is about 7% per year, and the incidence of the development of an AHI of 15 events per hour is about 2% per year. In this study, 47 of 286 eligible participants (16%; 95% CI, 13 to 21%) had a second-study AHI of at least 10, and 29 participants (10%; 95% CI, 7 to 14%) had a secondstudy AHI result of at least 15. (The authors skirted the issue of what constitutes OSA syndrome, referring instead to sleep-disordered breathing or to absolute AHIs). The Cleveland Family Study 14 also suggested that with aging, male gender and BMI become less important as risk factors for OSA. Of note, Brazilian investigators 27 applied the Berlin questionnaire to 10,101 truck drivers and reported that 26% were at high risk for OSA. We found a bell-shaped relationship between age and high risk for sleep apnea (Fig 1), with a declining risk after the age of 65 years. Some previous work 15,28,29 indicates that the risk of sleep apnea increases linearly with aging, but other data 30,31 have demonstrated a decline after mid-life. In general, studies of clinical populations have tended to find a peak prevalence of clinically significant sleep-disordered breathing in middle age, but population-based studies have found increasing levels of sleep-disordered breathing with aging. One possible explanation for this discrepancy has been suggested by Bixler et al 30 as follows: Severity of sleep apnea, as indicated by both number of events and minimum oxygen saturation, decreased with age when any sleep apnea criteria were used and when controlling for BMI. The study shows that the prevalence of sleep apnea tends to increase with age but that the clinical significance (severity) of apnea decreases. This notion is supported by recent work from Lavie et al, 9 who found that all-cause mortality for a given severity of sleep apnea was greater for men 50 years of age than those 50 years of age. In other words, describing severity of sleep apnea by the simplified metric of the apnea-hypopnea index does not reliably capture the severity of hypoxemia, the duration of events, associated cardiac arrhythmias, and degree of sleep disruption that may be associated. The 2005 NSF poll did not include a representative sampling of ethnic groups currently present in the United States despite efforts to do so. Only 16% of the sample reported here was nonwhite. This is an unfortunate problem with telephone polls and is also a problem with much of the published literature about sleep apnea prevalence to date. To the extent that the poll sample underestimated the true ethnic representation in this country, it may also underestimate the prevalence of sleep apnea. Ethnicity appears to play a role in the development of sleepdisordered breathing. Asian, 32 34 African-American, 35,36 and Hispanic 25 individuals may be at increased risk for sleep apnea, even when controlling for other important risk factors. Another weaknesses is that the height and weight data were self-reported (as were all of the data), and could be inaccurate. This, unfortunately, is a problem common to all telephone interviews. The 2005 NSF poll indicates that one in four Figure 3. Prevalence of chronic illnesses among individuals with high-risk Berlin questionnaire score. Individuals were asked, Have you ever been told by a doctor that you have any of the following medical conditions... 784 Original Research

Americans is at high risk for OSA, with increasing risk up to the age of 65 years. Considering the serious adverse health and quality-of-life consequences of sleep-disordered breathing, efforts to expedite diagnosis and treatment are urgently needed. Berlin Questionnaire Appendix The following questions were asked in the course of the telephone survey. Responses were recorded and section sums tallied. If two or more sections were positive, the individual was considered the have a high-risk Berlin score. Section 1 1.Do you snore? b. No (0) c. Don t know/refused (0) 2.If you snore, your snoring is: a. Slightly louder than breathing (0) b. As loud as talking (0) c. Louder than talking (0) d. Very loud; can be heard in adjacent rooms (1) e. Don t know/refused (0) 3.How often do you snore? b. 3 to 4 nights per week (1) c. 1 to 2 nights per week (0) d. 1 to 2 nights per month (0) e. Never or nearly never/don t know (0) 4. Has your snoring ever bothered other people? b. No/don t know/refused (0) 5. Has anyone noticed that you quit breathing during your sleep? a. Nearly every day (2) b. 3 to 4 times a week (2) f. Add scores from questions 1 to 5: g. If 2, check here Section 2 6.How often do you feel tired or fatigued after your sleep? b. 3 to 4 times a week (1) 7.During your wake time, do you feel tired, fatigued, or not up to par? b. 3 to 4 times a week (1) 8.Have you ever nodded off or fallen asleep while driving a vehicle? b. No/don t know/refused (0) 9.If yes, how often does it occur? b. 3 to 4 times a week (1) f. Add scores from questions 6 to 9: g. If 2, check here 10.Do you have high BP? b. No (0) c. Don t know/refused (0) 11.What is your height? 12.What is your weight? 13.How old are you? 14.Are you a. Male? b. Female? 15. Body mass calculation (by interviewer) a. Is BMI 30 kg/m 2? i. Yes (1) ii. No (0) b. Add scores from questions 10 to 15: c. If 1, check here d. If 2 sections are checked, subject is at risk for sleep apnea (ie, high-risk Berlin score). References 1 Nieto FJ, Young TB, Lind BK, et al. Association of sleepdisordered breathing, sleep apnea, and hypertension in a large community-based study. JAMA 2000; 283:1829 1836 2 Peppard PE, Young T, Palta M, et al. Prospective study of the association between sleep-disordered breathing and hypertension. N Engl J Med 2000; 342:1378 1384 3 Peker Y, Hedner J, Norum J, et al. Increased incidence of cardiovascular disease in middle-aged men with obstructive sleep apnea: a 7-year follow-up. Am J Respir Crit Care Med 2002; 166:159 165 4 Kaneko Y, Floras JS, Usui K, et al. Cardiovascular effects of continuous positive airway pressure in patients with heart failure and obstructive sleep apnea. N Engl J Med 2003; 348:1233 1241 5 Yaggi HK, Concat J, Kernan WN, et al. Obstructive sleep apnea as a risk factor for stroke and death. N Engl J Med 2005; 343:2034 2041 6 Babu AR, Herdegen J, Fogelfeld L, et al. Type 2 diabetes, glycemic control, and continuous positive airway pressure in obstructive sleep apnea. Arch Intern Med 2005; 165:447 452 7 Goncalves MA, Guilleminault C, Ramos E, et al. Erectile dysfunction, obstructive sleep apnea syndrome, and nasal CPAP treatment. Sleep Med 2005; 6:333 339 8 Campos-Rodriguez F, Pena-Grinan N, Reyes-Nunez N, et al. Mortality in obstructive sleep apnea-hypopnea patients treated with positive airway pressure. Chest 2005; 128:624 633 9 Lavie P, Lavie L, Herer P. All-cause mortality in males with sleep apnoea syndrome: declining mortality rates with age. Eur Respir J 2005; 25:514 520 10 Marin JM, Carrizo SJ, Vicente E, et al. Long-term cardiovascular outcomes in men with obstructive sleep apnoea-hypopnoea with or without treatment with continuous positive airway pressure: an observational study. Lancet 2005; 365: 1046 1053 www.chestjournal.org CHEST / 130 / 3/ SEPTEMBER, 2006 785

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