Neck circumference as a measure of central obesity: Associations with metabolic syndrome and obstructive sleep apnea syndrome beyond waist circumference

Background & aims: To investigate the relationship of neck circumference (NC) to metabolic syndrome (MetS) and obstructive sleep apnea syndrome (OSAS) and whether it adds information to that provided by waist circumference. Methods: Cross-sectional analysis of a population sample of 1912 men and women, aged 55.1 +/- 12 years, representative of Turkish adults. MetS was identified based on modified criteria of the ATP-III, OSAS when habitual snoring and episodes of apnea were combined with another relevant symptom. Results: NC measured 36.7 (+/- 3.5) cm in the total sample. It was significantly Correlated with numerous risk factors, above all body mass index and waist girth (r >= 0.6), homeostatic model-assessed insulin resistance, blood pressure and, inversely, with smoking status and sex hormone-binding globulin. Sex- and age-adjusted NC was associated significantly with MetS, at a 2-3-fold increased likelihood for 1 standard deviation (SD) increment. After further adjustment for waist circumference and smoking status, a significant residual odds ratio (OR, 1.13 [95% CI 1.08; 1.19]) persisted, corresponding to ORs of 1.53 and 1.27 in males and females, respectively, for 1 SO increment. Even when adjusted for all MetS components, a residual OR (1.08 [95% CI 1.000; 1.17]) remained. Sex- and age-adjusted NC was associated significantly also with OSAS in genders combined, independent of waist girth, yielding all added OR of 1.3 for 1 SD increment. Conclusions: NC contributes to MetS likelihood beyond waist circumference and the MetS components. Regarding association with OSAS, NC is of greater value than WC among Turkish men, not women. (c) 2008 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.