Validity of the Epworth Sleepiness Scale as a Screening Tool for Obstructive Sleep Apnea

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1 The Laryngoscope VC 2016 The American Laryngological, Rhinological and Otological Society, Inc. Validity of the Epworth Sleepiness Scale as a Screening Tool for Obstructive Sleep Apnea Lauren B. Bonzelaar, MD; Anna M. Salapatas, MS; Junhua Yang, BEc; Michael Friedman, MD Objectives/Hypothesis: To determine whether the Epworth Sleepiness Scale (ESS) can be improved by having a bed partner or roommate ( partner ) also fill out the questionnaire; and to assess the applicability of the eight items in the questionnaire, particularly in an urban population. Study Design: Retrospective chart review. Methods: A retrospective chart review was conducted to identify charts of subjects with an ESS score collected from both the subject and a partner. Consensus scores were also identified. Self-reported ESS scores were compared to partner and consensus ESS scores. The number of subjects who did not drive was determined. Results: One hundred consecutive charts were included in this study. Mean ESS score was significantly higher when scored by the partner ( ) compared to the subject ( ). In 73% of cases, the subject underestimated their score compared to the score given by the partner. The mean difference in score was Mean consensus ESS score was Using an ESS score of 10 as abnormal, subject scores did not correlate with the presence of obstructive sleep apnea (OSA; P 5.095). Partner and consensus scores, however, did correlate with the presence of OSA (P and P 5.039, respectively). Thirty-five percent of our subjects did not drive. Conclusions: The difference in mean ESS score obtained from the subject compared to partner implies that this diagnostic form should be completed as a consensus between the patient and partner to provide a more accurate score. Key Words: Epworth Sleepiness Scale, validity, obstructive sleep apnea, daytime sleepiness, apnea hypopnea index. Level of Evidence: 4 Laryngoscope, 127: , 2017 INTRODUCTION The Epworth Sleepiness Scale (ESS) was introduced in 1991 and validated as a new method for measuring daytime sleepiness. Since then it has been widely accepted and used as a screening tool for obstructive sleep apnea (OSA). This questionnaire requires the subject to rate, on a scale from 0 to 3, his/her chances of dozing in eight different situations. These scenarios were chosen to differ in their soporific nature. 1 The reproducibility of ESS scores was initially described to be as reliable as the Multiple Sleep Latency Test (MSLT) or Maintenance of Wakefulness Test (MWT). 2 Despite three early studies by Dr. Johns, who developed the tool, and showed that ESS scores significantly correlated with severity of OSA, 1,3,4 many studies have not been able to validate their data. Twenty publications have From the Chicago ENT: Advanced Center for Specialty Care (L.B.B., A.M.S., J.Y., M.F.) and Rush University Medical Center (M.F.), Chicago, Illinois, U.S.A. Editor s Note: This Manuscript was accepted for publication June 28, Institution where work was done: Chicago ENT: Advanced Center for Specialty Care. Presented orally at the Triological Society Combined Otolaryngology Spring Meeting, Chicago, Illinois, U.S.A., May 18 22, The authors have no funding, financial relationships, or conflicts of interest to disclose. Send correspondence to Michael Friedman, MD, FACS, Chicago ENT: Advanced Center for Specialty Care, 30 North Michigan Ave., Suite 1107, Chicago, IL mfriedman@chicagoent.com DOI: /lary demonstrated results questioning the correlation of ESS with polysomnographic (PSG) findings and MSLT. Among other issues with this tool, we hypothesize that the ESS score obtained from the patient may be less than accurate and that partner-assessed ESS scores will lead to more accurate results. The ESS was presented as a simple selfadministered questionnaire. 1 It is well recognized that denial of symptoms is extremely common in patients with OSA. Most sleep physicians attempt to obtain an accurate history from a bed partner or family member to overcome the element of denial. We hypothesize that the results of the ESS questionnaire will be different if obtained from a bed partner versus the patient. In addition, we suspect that when the scores are widely different, the bed partner score will be more closely correlated to AHI. MATERIALS AND METHODS Patient Selection Western Institutional Review Board (Puyallup, WA) approved this case series and chart review with exempted informed consent and Health Insurance Portability and Accountability Act waiver. A retrospective chart review of all consecutive patients treated at the otolaryngology clinic for upper airway symptoms was conducted between June 2015 and April All patients are routinely screened for OSA. Inclusion criteria were 1) 18 years of age; 2) patient (hereafter described as subject ) independently rated daytime sleepiness using the ESS questionnaire; and 3) bed partner, roommate, or 525

2 Fig. 1. Adapted Epworth Sleepiness Scale questionnaire. This version of the questionnaire is used in our office and includes modifications including specification of patient versus spouse/roommate, and driver versus nondriver. other household member (hereafter described as partner ) independently rated the subject s daytime sleepiness using an adapted version of the ESS questionnaire (Fig. 1). Using this criteria, 100 consecutive charts were identified with data from both the subject and a partner. Forty-seven of these also had a consensus ESS score available. All subjects were new referrals and had not yet undergone any medical or surgical treatment of OSA at the time of ESS collection. Subjects evaluated for other sleep disorders such as narcolepsy, periodic limb movement disorder, restless leg syndrome, or idiopathic hypersomnia were excluded. Data Collection Data collection included basic demographics (age, gender, body mass index [BMI], and marital status), daytime sleepiness, snoring intensity, and severity of OSA. Symptoms of daytime somnolence were measured using the ESS. ESS questionnaires 526

3 TABLE I. Patient Demographics and Mean ESS Scores. Variable ESSs* ESSp* Difference, ESSp 2 ESSs* P, t test Total, n Gender Male, n Female, n OSA Yes, n No, n AHI Mild, n Moderate, n Severe, n Probability by t test measures whether the difference between ESSs and ESSp is significant within each variable. *Data are expressed as mean 6 standard deviation. P <.05. AHI 5 apnea hypopnea index; ESS 5 Epworth Sleepiness Scale; ESSp 5 ESS score of the partner; ESSs 5 ESS score of the subject; OSA 5 obstructive sleep apnea. were completed by subjects suspected of having OSA, as part of standard practice upon consultation at an otolaryngology clinic. ESS scoring was also completed independently by a partner, as part of standard clinical practice. Consensus data were often identified once both completed their individual scoring. As an added measure of accuracy, the ESS questionnaire used at the clinic asks subjects if they drive (yes/no). Subjects who screened positive for OSA with the STOPbang questionnaire were often referred for a one-night baseline formal laboratory polysomnographic evaluation. PSG was performed with a standard 16-channel overnight test in a sleep laboratory or a ResMed home sleep study, and reports were read by a physician certified in sleep medicine. Apnea was defined as 90% decrease in airflow amplitude for 10 seconds. Hypopnea was defined as 50% decrease in the airflow amplitude for 10 seconds with an oxygen desaturation of 4%. Subjects with an apnea hypopnea index (AHI) > 5 were diagnosed with OSA. Severity of OSA was categorized as follows: mild, 5 < AHI < 15; moderate, 15 AHI < 30; severe, AHI 30 events/ hr (American Academy of Sleep Medicine criteria). Statistical Analysis All statistical analyses were performed using SAS v9.4 (SAS Institute, Cary, NC). Continuous data are displayed as mean 6 standard deviation and categorical data as n (%). Student t tests were utilized to identify differences in ESS scores between the subjects and their partners. v 2 tests were used to test the association between categorical variables. Pearson q correlations were calculated to determine relationships and strong interactions between variables. Friedman analysis of variance was used to assess within OSA severity subgroups (none, mild, moderate, severe). The Shapiro Wilk test, the skewness and kurtosis values, and the Q-Q plots suggest normality of data. Statistical significance was accepted for P <.05. Literature Review Studies evaluating the validity of the ESS questionnaire as a tool to identify OSA were obtained using the search terms Epworth Sleepiness Scale validation, Epworth Sleepiness Scale validity, and Epworth Sleepiness Scale reliability. Studies included were those which assessed patient versus partner ESS scores, correlation of ESS with AHI, and correlation of ESS with sleep latency. Studies initially missing from our literature search that were included in Kendzerska et al. s systematic review 5 were added to our review when applicable (if they assessed ESS in relation to AHI or sleep latency). Only studies with full text available in English were assessed. Only studies validating ESS for use in OSA or suspected OSA were used. Therefore, studies assessing validity of ESS in the general population, among other sleep disorders (narcolepsy, insomnia), or within specific comorbid populations (chronic obstructive pulmonary disease, heart disease) were not assessed. Studies validating an alternate version of the ESS in another language were excluded (21 studies). RESULTS Data from 100 total subjects evaluated at the otolaryngology clinic were included in this analysis. Subjects were predominantly male (n 5 67), the mean age was years, and the average BMI was kg/m 2. Of the 100 subjects, 72 had OSA, with mean AHI of events/hr. Of the 100 paired ESS responders, 68 shared the same room with their partner. Of the 100 subjects, 35 reported that they did not drive. On average subjects scored their daytime sleepiness as , whereas the partners scored it an average of (P <.000; Table I, Fig. 2). The ESS consensus score had a mean of , with 89% of the data corresponding with the higher of the two scores, predominantly the partner s (Table I, Fig. 2). Seventythree subjects reported a lower ESS than their partner, whereas 14 subject partner pairs showed no difference in ESS scoring, and 13 subjects scored higher than their partner (Fig. 3). Using the formula difference 5 ESSp 2 ESSs, where ESSp is the partner ESS score and ESSs is the subject ESS score, the mean difference in ESS was , and the range of scores was 26 to 14. Of the 73 subjects who scored lower than their partners, the mean difference in ESS score was

4 survey and relies on the patient to recount his or her symptoms, the question has been posed as to whether the patient is a reliable source. Any subjective questionnaire is open to unintended bias, purposeful falsification, or simply the inability of the subject to read and comprehend the questionnaire. 2 Fig. 2. Mean Epworth Sleepiness Scale (ESS) separated by cohort. Mean ESS of subjects (ESSs) is ; mean ESS of partners (ESSp) is ; mean consensus ESS (ESSc) is [Color figure can be viewed in the online issue, which is available at The mean difference in ESS for male subjects was (P <.000), and it was (P 5.005) for female subjects. Males were more likely to score lower than their partners (v , P 5.003). Partners who shared the same room as the subject did not score statistically differently from other roommates/household members. When comparing individual ESS scores to AHI, both subject and partner ESS scores showed significant weak/moderate positive correlations with AHI (q and q , respectively). Based on the definition of an abnormal ESS, a cutoff of 10 was used as an indicator of OSA. Fifty-five partners (55%) scored their corresponding subject equal to or above 10, whereas only 29 subjects (29%) scored themselves above the cutoff. Based on the association between AHI > 5 and an ESS 10 cutoff, partner and consensus ESS scores were an indicator of OSA (P and P 5.039, respectively), whereas subject scores were not (P 5.095). DISCUSSION Daytime somnolence is a common chief complaint associated with OSA and other sleep disorders. In addition to objective OSA findings, subjective reports of excessive daytime sleepiness are an important aspect of each patient s course of management. Therefore, a simple standardized test is necessary for measuring overall levels of daytime sleepiness that is independent of shortterm variations in somnolence. The ESS was initially produced as a simple, selfadministered questionnaire, providing a quick measurement of a subject s general level of daytime sleepiness. 1 The ESS is commonly used by insurance companies as a screening tool to identify the medical necessity of sleep testing or treatment for OSA. The assumption is that patients with an ESS score of <10 may not require polysomnography and do not require surgical treatment for OSA. Many reports, however, have found that the selfadministered portion may not be as accurate as initially described. Because the questionnaire is a subjective 528 Sleep Latency In a literature review of 33 articles assessing the validity of ESS as a tool for the diagnosis of OSA (Table II), 13 studies compared ESS scores to objective sleep latency measures using MSLT results. The MSLT has been established as the most objective test of daytime sleepiness, with obvious comparisons being made with subjective ESS scores. Eleven studies have shown sleep latency measured via MSLT to be correlated with ESS scores. 1,2,5 13 That is, as ESS score increases, sleep latency decreases. Conversely, two studies have shown sleep latency not to be correlated with ESS scores. 14,15 Sleep latency can also be measured via PSG or the MWT. Although these methods have been studied less in the context of daytime sleepiness in OSA, one study measuring sleep latency via PSG 1 and four studies measuring sleep latency via MWT 5,7,16,17 have shown inverse correlations with ESS score. However, conflicting results were demonstrated in two studies showing no correlation between ESS and sleep latency, one measured via PSG 18 and the other measured by MWT. 19 Overall evidence points toward a strong correlation between objectively measured sleep latency and subjectively obtained ESS scores. Although this is reassuring, we must remember that we rarely send our OSA patients for MSLT or MWT. More importantly, treatment of OSA is not based on MSLT or MWT results. However, Fig. 3. Differences in Epworth Sleepiness Scale (ESS) score between subject and partner, based on the formula difference 5 ESSp 2 ESSs, where ESSp 5 partner ESS score and ESSs 5 subject ESS score. Each point represents a subject patient pair. White diamonds represent subjects with a lesser ESS score than their partner (n 5 73), black diamonds represent subject partner pairs with no difference in ESS scores (n 5 14), and gray diamonds represent subjects with a greater ESS score than their partner (n 5 13). The range of difference in ESS scores is 26 to 14, with negative numbers representing subjects scoring higher than their partner, and positive numbers representing subjects scoring lower than their partner.

5 TABLE II. Literature Review of Studies Assessing the Validity of the ESS as a Screening Tool for OSA. Ref Author Year Patient vs. Partner ESS Score AHI SL-MSLT SL-MWT SL-PSG Johns 1991 SC SC SC Johns 1993 SC Johns 1994 SC SC Kingshott 1995 SC NSC Chervin 1997 NSC SC Kingshott 1998 NSC SC SC Olson 1998 NSC SC Chervin 1999 NSC NSC Osman 1999 NSC Benbadis 1999 NSC Gottlieb 1999 SC Sangal 1999 NSC Chung 2000 NSC SC Giudici 2000 NSC NSC Gottlieb 2000 SC Walter 2002 SC SC Leng 2003 SC Banks 2004 SC Weaver 2004 NSC Weaver 2005 NSC Kaminska 2010 SC SC Sharkey 2010 NSC Ugur 2011 SC Danzi- Soares 2012 NSC Hesselbacher 2012 SC Sunwoo 2012 SC Damiani 2013 NSC Cai 2013 SC SC Nishiyama 2014 NSC Kendzerska 2014 NSC* Weak SC Moderate SC Li 2014 NSC SC SC Zou 2013 SC Ryu 2016 NSC *Strong level of evidence. Moderate level of evidence. AHI 5 apnea hypopnea index; ESS 5 Epworth Sleepiness Scale; NSC 5 no significant correlation; OSA 5 obstructive sleep apnea; Ref 5 reference number; SC 5 significant correlation; SL-MSLT 5 sleep latency measured via the Multiple Sleep Latency Test; SL-MWT 5 sleep latency measured via the Maintenance of Wakefulness Test; SL-PSG 5 sleep latency measured via polysomnography. the evidence supporting the value of ESS in correlation with the presence or severity of OSA is weak. OSA Severity Because AHI is an essential objective finding of OSA severity, its relation to ESS score is equally important to assess. In our literature review of 33 studies assessing the validity of the ESS questionnaire, 27 evaluated ESS in relation to AHI. Whereas 11 studies demonstrated a significant correlation between AHI and ESS score, 1,4,12,13,17, studies demonstrated no correlation between the two variables. 5 9,14,18,26 34 Furthermore, a systematic review of 35 articles established with a strong level of evidence that no significant relationship exists between ESS score and AHI. 5 However, 24 of these 27 articles only analyzed self-ranked ESS scores in comparison to AHI. Although we would not necessarily expect ESS and AHI to be related, as they measure different aspects of sleep apnea, we also know that severity of disease cannot be based upon a patient s self-assessed ESS score. We know based on our results that only partner- and consensus-ranked ESS scores 10 correlate with the presence of OSA. Patient Versus Partner ESS Scores In 1994, Johns was the first to assess daytime sleepiness by evaluating ESS determined by both the patient and the bed partner. 2 Johns demonstrated no 529

6 significant difference between the two paired scores. One year later, Kingshott et al. also assessed patients sleepiness by independently rated patient and partner ESS scores. Although they found that patient and partner ESS scores were not significantly different, they also found ESS scores were not significantly related to severity of OSA, 26 which was contrary to previous correlations (r , P <.001) found by other investigators. 4 Patient partner ESS correlations were not reassessed until 2002, when it was reconfirmed that no significant difference exists between the paired ESS scores. 22 However, in 2014, for the first time, Li et al. demonstrated a significant difference in individual paired ESS scores between patient and partner. 13 This disparity in results raises some questions that we sought to answer with our retrospective chart review. Our results demonstrated significant differences between subject and partner scores. This difference may suggest that the 29 other articles using only patientevaluated ESS scores to validate the ESS questionnaire may have had different results if partner ESS scores were used instead. Our results suggest that only the partner or a consensus ESS score is an indicator of OSA. Nondriver ESS Scores As an additional measure of the ESS questionnaire validity, our study assessed the significance of the eightitem score for nondrivers. We found that in our urban population, many people take public transportation, in which case the eighth item of the questionnaire (In a car, while stopped for a few minutes in traffic) would not apply. In these instances, a score out of 24 would not be accurate, and instead a maximum score of 21 should be used. Based on the typical 24-maximum, an abnormal ESS of 10 of 24 would equate to an 8.75 on the 21-point scale. We then applied this new abnormal (ESS > 8) to nondrivers to assess the applicability to the presence of OSA. Using an ESS score of 8 as the cutoff for nondrivers (n 5 35), 15 partners (42.9%) scored their corresponding subject above the cutoff, whereas only eight subjects (22.9%) scored themselves above the cutoff. More importantly, only three of the 15 partner ESS scores would have qualified for OSA in the cutoff 10 group, and none of the eight subjects ESS scores qualified for OSA in the cutoff 10 group. Our results indicate that of those who do not drive, an ESS cutoff score of >8 may be a better indicator of OSA. Because item 8 on the questionnaire does not apply to nondrivers, their ESS score should be based on a maximum score of 21 instead of 24. As such, their cutoff value for OSA may be lowered to >8. This concept is especially important in big cities, or areas with ample access to public transport. CONCLUSION Using an abnormal ESS (10) as an indicator of OSA, partner ESS scores were predictive of OSA, whereas subject ESS scores were not predictive. 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