Neck circumference is a predictor of metabolic syndrome and obstructive sleep apnea in short-sleeping obese men and women

Abstract

Background: The constellation of metabolic syndrome, although controversial with regard to its clinical usefulness, is epidemiologically related to increased diabetes risk and cardiovascular mortality. Our goal was to investigate the associations among neck circumference (NC), obstructive sleep apnea syndromes (OSAS), and metabolic syndrome in obese men and women sleeping less than 6.5 hr per night.

Methods: This was a cross-sectional study of obese men and premenopausal obese women sleeping less than 6.5 hr per night. We enrolled 120 individuals (92 women), age 40.5±6.9 years and body mass index (BMI) 38.6±6.5 kg/m(2). Metabolic syndrome severity was assessed by a score and OSAS was defined as a respiratory disturbance index (RDI) ≥5. Metabolic end endocrine parameters were measured, and sleep duration was determined by actigraphy and validated questionnaires.

Results: Metabolic syndrome was found in 41% and OSAS in 58% (28% had both). Subjects with metabolic syndrome were 3 years older and more often Caucasian; they had higher RDI scores, larger NC, more visceral fat, lower serum adiponectin, higher 24-hr urinary norepinephrine (NE) excretion, and lower growth hormone concentrations. A NC of ≥38 cm had a sensitivity of 54% and 58% and a specificity of 70% and 79% in predicting the presence of metabolic syndrome and OSAS, respectively. RDI, adiponectin, and NC accounted for approximately 30% of the variability in the metabolic syndrome score, as estimated by an age-, gender-, and race-corrected multivariate model (R(2)=0.376, P<0.001).

Conclusion: Greater NC is associated with OSAS and metabolic syndrome in short-sleeping obese men and premenopausal obese women. Addition of NC to the definition of metabolic syndrome should be considered and needs to be validated in future studies.

FIG. 1.

Percentage and number of participants presenting with individual metabolic syndrome criteria. MetS, metabolic syndrome; HDL, high-density lipoprotein; N.S., not significant.

FIG. 2.

Relationships between respiratory disturbance index (RDI), metabolic syndrome score, and adiponectin. Note the use of safe logarithmic scale, namely, LOG₁₀(1+RDI) on the x axis. MetS, metabolic syndrome; RDI, respiratory disturbance index.

FIG. 3.

Relationship between waist circumference, neck circumference, and respiratory disturbance index (RDI), as well as waist circumference, neck circumference (NC), and metabolic syndrome score (n=100). Note the use of safe logarithmic scale, namely, LOG₁₀(1+RDI) on the y axis of A and B. MetS, metabolic syndrome; RDI, respiratory disturbance index.

FIG. 4.

Received operating characteristic (ROC) curves for the diagnostic performance of waist circumference, visceral fat, and neck circumference (NC) measurements regarding metabolic syndrome and obstructive sleep apnea syndromes (OSAS) in 92 short-sleeping obese women. Thin lines show 95% confidence intervals, arrows point at the optimal cutoff as defined by the Youden index for diagnostic sensitivity and specificity, and area under the curve (AUC).