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The STOP-Bang score (derived from the STOP-Bang questionnaire) is an 8-item validated clinical screening instrument developed by Dr. Frances Chung and colleagues at the University Health Network (University of Toronto) and published in Anesthesiology (2008) to stratify a patient’s risk of obstructive sleep apnea (OSA). Combining four self-reported symptom and comorbidity questions (STOP: Snoring, Tiredness, Observed apnea, high blood Pressure) with four objective anthropometric and demographic measures (Bang: BMI, Age, Neck circumference, Gender), the STOP-Bang questionnaire produces a total score from 0 to 8 points.
In preoperative anesthesiology clinics, sleep medicine triage, and perioperative patient safety research—alongside airway and neurological assessment tools such as the Glasgow Coma Scale and Clinical Frailty Scale—the STOP-Bang score is the primary screening standard endorsed by the Society of Anesthesia and Sleep Medicine (SASM) to identify patients with undiagnosed moderate-to-severe OSA before general anesthesia or procedural sedation.
What Is the STOP-Bang Score? The 8 Questionnaire Items and Scoring Rules
Each of the eight items on the STOP-Bang questionnaire is scored dichotomously as Yes = 1 point or No = 0 points, yielding an integer total score from 0 to 8:
| Acronym Letter | Clinical Domain | Exact Screening Question / Anthropometric Criterion | Scoring Rule |
|---|---|---|---|
| S | Snoring | Do you Snore loudly (louder than talking or loud enough to be heard through closed doors)? | Yes = 1, No = 0 |
| T | Tiredness | Do you often feel Tired, fatigued, or sleepy during the daytime (such as falling asleep during driving or talking to someone)? | Yes = 1, No = 0 |
| O | Observed Apnea | Has anyone Observed you stop breathing or choking/gasping during your sleep? | Yes = 1, No = 0 |
| P | Blood Pressure | Do you have or are you being treated for high blood Pressure (hypertension)? | Yes = 1, No = 0 |
| B | Body Mass Index (BMI) | Is Body Mass Index (BMI) greater than 35 kg/m²? | > 35 kg/m² = 1, ≤ 35 kg/m² = 0 |
| A | Age | Is Age over 50 years old? | > 50 years = 1, ≤ 50 years = 0 |
| N | Neck Circumference | Is Neck circumference greater than 40 cm (approx. 16 inches, measured around the cricothyroid membrane)? | > 40 cm = 1, ≤ 40 cm = 0 |
| G | Gender | Is Gender Male? | Male = 1, Female = 0 |
Two-Step STOP-Bang Risk Stratification Cutoffs and Diagnostic Sensitivity
In the original surgical validation study by Chung et al. (Anesthesiology, 2008; 108(5):812–821) against overnight laboratory polysomnography (PSG) using an Apnea-Hypopnea Index (AHI) threshold, a STOP-Bang cutoff of ≥ 3 points demonstrated a sensitivity of 83.6% for any OSA (AHI > 5), 92.9% for moderate-to-severe OSA (AHI > 15), and 100% for severe OSA (AHI > 30), with a high negative predictive value (NPV) of 90.5% for excluding moderate-to-severe OSA when the score is 0–2.
Because a score of 3 or 4 has high sensitivity but modest specificity, Chung et al. (British Journal of Anaesthesia, 2012; Chest, 2016) established a validated two-step STOP-Bang risk stratification algorithm that reclassifies specific intermediate-score patients into the High-Risk tier:
| Risk Tier | Total STOP-Bang Score / Combination Criteria | Clinical Probability of Moderate-to-Severe OSA (AHI > 15) | Recommended Preoperative & Clinical Action |
|---|---|---|---|
| Low Risk of OSA | 0 to 2 points | Low probability (< 15% in surgical cohorts; high NPV excludes severe OSA) | Proceed with standard perioperative care; routine sleep study not required prior to surgery. |
| Intermediate Risk of OSA | 3 to 4 points (and does not meet any Step 2 High-Risk combination rule below) | Intermediate probability | Evaluate comorbid cardiopulmonary disease (e.g., heart failure, pulmonary hypertension, obesity hypoventilation) and consider venous serum bicarbonate (HCO3− ≥ 28 mmol/L) or home sleep apnea testing (HSAT). |
| High Risk of OSA | 5 to 8 points, OR ≥ 2 positive STOP items (out of 4) PLUS at least one of: • Male gender (G = 1) • BMI > 35 kg/m² (B = 1) • Neck circumference > 40 cm (N = 1) |
High probability (each point increase from 3 to 7+ progressively increases the probability of severe OSA above 50%–70%) | Institute presumptive OSA perioperative precautions: regional/multimodal opioid-sparing analgesia, CPAP/BiPAP readiness in PACU, continuous pulse oximetry/capnography, and outpatient sleep medicine referral. |
Serum Bicarbonate Addition for Intermediate-Risk Patients (Score 3–4)
In patients who score 3 or 4 on the STOP-Bang questionnaire without meeting the anthropometric high-risk combinations, chronic nocturnal hypoventilation and hypercapnia often cause compensatory renal retention of bicarbonate. As validated by Chung et al., combining a STOP-Bang score of ≥ 3 with a routine preoperative metabolic panel showing serum HCO3− ≥ 28 mmol/L increases specificity for moderate-to-severe OSA from 37% to 85.2%.
How Is the STOP-Bang Score Used in Clinical Research and Preoperative Healthcare Workflows?
In hospital perioperative medicine, ambulatory surgery centers (ASCs), and clinical informatics, the STOP-Bang score is embedded directly into the pre-anesthesia evaluation module of the electronic medical charting system:
- Automated EHR Calculation from Flowsheets + Patient Intake: Because four of the eight items—BMI (calculated automatically from vital signs height and weight), Age (calculated from DOB), Gender (from demographics), and Pressure (from ICD-10-CM
I10hypertension on the problem list or antihypertensive medications)—already reside in discrete EHR fields, digital patient intake forms only need to prompt the patient for the three subjective questions (S, T, O) and prompt the intake nurse to measure Neck circumference. - Perioperative Risk Mitigation & PACU Monitoring Protocols: Patients stratified as High Risk (STOP-Bang ≥ 5 or Step 2 positive) are flagged on the anesthesia intraoperative record for difficult mask ventilation / intubation readiness, semi-upright extubation, multimodal non-opioid analgesia (minimizing opioid-induced central respiratory depression and pharyngeal muscular hypotonia), and extended Post-Anesthesia Care Unit (PACU) monitoring for recurrent oxygen desaturation or apnea events.
- Clinical Research Trial Screening & Covariate Stratification: In sleep medicine, bariatric surgery, and cardiovascular clinical trials, the STOP-Bang score serves as a rapid pre-screening gate before confirmatory home sleep apnea testing (HSAT) or in-laboratory polysomnography (PSG).
