Introduction

Obstructive sleep apnea (OSA) is strongly correlated with cardiovascular disorders (e.g., myocardial infarction, dysrhythmias, and congestive heart failure). OSA leads to desaturations, arousals, and wide swings in intrathoracic pressure during apneic episodes, resulting in increased sympathetic tone in patients with OSA that may persist into the day. Such desaturations, arousals, and heightened sympathetic activity accelerate atherosclerosis by causing inflammatory and cellular processes that produce cardiac stress and other cardiovascular mechanisms of disease.

As there is increasing evidence that treatment of OSA facilitates management of cardiovascular diseases and potentially improves cardiovascular outcomes, recognizing and treating OSA is vital to reducing the disease burden of cardiac disorders.

Diagnosing OSA, however, may prove challenging for the non-sleep specialist. Several screening tools exist to aid in identification of these patients. This article aims to review available screening tools and provide recommendations for the appropriate screening tool based on ease of use and sensitivity.

Screening Tools for Sleep Apnea

The increasing importance of sleep apnea in mortality and morbidity reduction facilitated the development of several screening tools currently used. The most important and clinically useful screening tool exhibits the qualities of being easily administered and incorporated into clinic as well as having the highest sensitivity and specificity. There are four screening tools widely recognized as being fairly easy to administer: Stop, STOP-BANG (SB), Epworth Sleepiness Scale (ESS), and 4-Variable screening tool (4-V).

The Stop and STOP-BANG questionnaire consist of four and eight questions, respectively. The Stop portion of the questionnaire consists of four yes/no self-answer questions assessing snoring, tiredness, observed apneas, and high blood pressure. The BANG portion of the questionnaire adds clinically observed quantities, again with yes/no answers, including BMI > 35 kg/m², age >50 years, neck circumference >40 cm, and male gender (Table 1). Positive answers on two out of the four questions of Stop or three out of the eight questions for STOP-BANG indicate high risk for sleep apnea. The study has been validated and demonstrates high sensitivity with moderate specificity.¹ In comparison testing with the other three screening tools, STOP-BANG demonstrated the highest sensitivity in patients with moderate-to-severe sleep apnea based on polysomnography (i.e., diagnostic sleep study) with increasing sensitivity as severity of sleep apnea increased. The specificity of STOP-BANG, however, was the lowest compared to the other tests.² Stop testing demonstrated 95% specificity versus 96% sensitivity compared to STOP-BANG. Higher scores on the STOP-BANG questionnaire increased specificity but lowered sensitivity.³

Table 1: STOP-BANG Questionnaire: One Point Awarded for Each Question Answered With "Yes"

• Snoring: Do you snore loudly (louder than talking or loud enough to be heard through closed doors)?
• Tired: Do you often feel tired, fatigued, or sleepy during daytime?
• Observed: Has anyone observed you stop breathing during your sleep?
• Blood Pressure: Do you have or are you being treated for high blood pressure?
• BMI: BMI more than 35 kg/m²?
• Age over 50 years old?
• Neck circumference greater than 40 cm (around 16in, measured by staff)?
• Gender male?

Modified from Chung F, Yegneswaran B, Liao P, et al. STOP Questionnaire: a tool to screen patients for obstructive sleep apnea. Anesthesiology 2008:108;812-21.

The ESS assesses propensity to dozing and severity of daytime sleepiness in common daily situations based on eight self-administered questions with answers ranging from zero to three with zero indicating no chance of dozing and three indicating always dozing. A score of 10 or higher indicates excessive daytime sleepiness. The ESS has also been validated in several studies⁴ and, when compared with the aforementioned tests, demonstrates the second highest specificity at 67%, but only 50% specificity in patients with moderate and severe sleep apnea.

The 4-V is an equation consisting of four variables including gender, BMI, blood pressure, and self-reported snoring.⁵ The equation is as follows:

OSA = (gender*4) + (BMI category value) + (BP category value) + (snoring*4)

Predetermined values for BMI include <21, 21-22.9, 23-24.9, 25-26.9, 27-29.9, and 30 with assigned values of one to six respectively. The BP values are defined as systolic BP (SBP) <140 or diastolic BP (DBP) <90, SBP 140-159 or DBP 90-99, SBP 160-179 or DBP 100-109, or SBP >180 or DBP >110 with assigned values between one and four respectively. Regarding gender, males were scored with one while females received a score of zero. Values greater than 11 are positive. Values greater than 14 were also assessed. At values greater than 11, the sensitivity was 78% and the specificity was 41%, while at values greater than 14, the sensitivity was 51% and the specificity was 78%, the highest when compared to the other screening tools.

The Pataka study also assessed combination of screening tools to evaluate changes in sensitivity and specificity, but no statistical differences emerged with the various combinations.² Overall, the most sensitive screening tool and one of the easiest to administer quickly in clinic appears to be STOP-BANG, while the most specific is the 4-V. Of note, this study was performed in sleep clinic populations; no studies assessing sleep apnea screening tools in cardiac clinic populations exist.

Based on ease of use and currently available data, the authors of this commentary recommend the use of the STOP-BANG questionnaire over other tools at this time. The authors of this commentary also find the STOP-BANG fairly acceptable by referring physician practices, non-sleep physicians, other health care professionals, and patients overall in terms of ease of utility. Some authors have advocated higher scores (≥4 e.g.) to identify higher risk individuals.³

Conclusion

Obstructive sleep apnea is increasing in prevalence and significantly increases cardiovascular morbidity and mortality by increasing sympathetic tone, inflammatory mediators, and cardiac stress. Treating sleep apnea improves cardiac function and reduces complications related to hypertension, congestive heart failure, and atherosclerosis.

Several tools exist for screening patients for sleep apnea with variable degrees of ease of administration and sensitivity and specificity. The most sensitive and easy to administer screening tool appears to be the STOP-BANG questionnaire; utilization of this screening tool would improve identification of patients at high risk for sleep apnea (with higher scores identifying higher-risk patients). Treatment of OSA in patients identified in this manner may then aid the clinician to optimize cardiovascular disease management.

Keywords: Anesthesiology, Apnea, Arousal, Atherosclerosis, Blood Pressure, Body Mass Index, Cost of Illness, Heart Failure, Hypertension, Myocardial Infarction, Polysomnography, Prevalence, Self Report, Sensitivity and Specificity, Sleep Apnea Syndromes, Sleep Apnea, Obstructive, Snoring

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