TABLE VI.D.

Neck circumference (NC) measurement in the diagnosis of OSA

Study	Year		Study design	Study groups	Clinical endpoint	Conclusion
Agha et al.535	2017	3a	Systematic review and meta-analysis of predominantly case–control studies	Not applicable	Not applicable.	Adults with OSA had an increased weighted mean difference in NC compared with controls, in five case–control studies. The pooled mean change was 1.26 mm (0.64–1.88), with large heterogeneity found between studies.
Kim et al.138	2015	3b	Cross-sectional retrospective study	Cohort of snoring Asian patients	Neck circumference in Asian patients with OSA compared to individuals with simple snoring.	NC predicted OSA presence and severity.
Kushida et al.537	1997	4	Prospective cohort study	Consecutive patients referred for evaluation of sleep disorders	Evaluated measurements of the oral cavity with body mass index and NC, in predicting OSA.	A NC ≥ 40 cm is associated with OSA sensitivity of 61% and specificity 93%.
Stradling et al.533	1990	4	Prospective study	Men 35–65 years old GP registry	Registry study.	NC was an independent predictor of nighttime hypoxia events.
Adult Obstructive Sleep Apnea Task Force of the American Academy of Sleep Medicine513	2009	5	Guideline	Not applicable	Not applicable.	Features that may suggest the presence of OSA include increased NC (> 17 inch in men and > 16 inch in women).
Ahbab et al.528	2013	4	Cohort study	OSA adults	Evaluate NC and metabolic syndrome parameters in OSA patients.	NC in severe OSA was significantly higher than in mild–moderate OSA. NC was an independent risk factor for severe OSA (odds ratio [OR]: 1.55. 95% confidence intervals [CI]: 1.09–2.21, p = 0.01).
Chang et al.529	2013	4	Prospective cohort	Cohort of Chinese patients with snoring complaints in sitting position	Evaluate if snoring in a sitting position is a predictor of OSA in patients.	NC ≥40 cm as a predictor for OSA had sensitivity 48.6%, specificity 87.8%, and likelihood ratio 3.98.
Park et al.532	2014	4	Retrospective cohort	Non-obese Asian patients who underwent PSG	Evaluate association between body weight and obstructive sleep apnea even in patients who are not obese.	AHI found to be positively correlated with the NC. NC is independently associated with OSA.
Davies et al.530	1990	4	Prospective study	Cohort of patients referred for investigation of sleep disorders	Importance of NC, obesity, and radiographic pharyngeal dimensions for OSA.	NC of 42.5 cm (16.75 inch) for a 1.78 m (5 feet 10 inch) man) is 77% sensitive and 82% specific for significant OSA with positive predictive value (PPV) of 75%.
Yildirim et al.534	2015	4	Prospective	Cohort of patients with a BMI ≥ 30 and OSA symptoms	Evaluate anthropometric measurements with OSA.	Significant positive correlation between AHI and neck circumference.
Mirrakhimov et al.531	2013	3a	Systematic review	Not applicable	Not applicable.	Neck circumference is associated with OSA.
Santos et al.542	2019	4	Cohort study	Cohort civil servants 35–74 years	Compare BMI, several surrogate markers of body fat (in isolation or combined) and validated questionnaires for screening OSA.	Age and gender-adjusted NC (AUC = 0.733 [0.711–0.755]) had moderate accuracy as predictor for OSA.
Yusoff et al.538	2010	4	Prospective	Cohort randomly selected express bus drivers	Identifying factors or conditions related with OSA.	NC (OR = 1.31, 95% CI 1.18–1.46) was significantly associated with OSA status.