Background: Neck circumference, a proxy for upper-body sc fat, may be a unique fat depot that confers additional cardiovascular risk above and beyond central body fat.
Methods and Results: Participants with neck circumference measures who underwent multidetector computed tomography to assess visceral adipose tissue (VAT) were included [n = 3307, 48% women; mean age = 51 yr; mean body mass index (BMI) = 27.8 kg/m2; mean neck circumference = 40.5 cm (men) and 34.2 cm (women)]. Sex-specific linear regression models were used to assess the association between sd increase in neck circumference and cardiovascular disease (CVD) risk factors (systolic and diastolic blood pressure; total, low-density lipoprotein, and high-density lipoprotein cholesterol and triglycerides; and fasting plasma glucose, insulin, proinsulin, and homeostasis model assessment of insulin resistance). Neck circumference was correlated with VAT [r = 0.63 (men); r = 0.74 (women); P < 0.001] and BMI [r = 0.79 (men); r = 0.80 (women); P < 0.001]. After further adjustment for VAT, neck circumference was positively associated with systolic blood pressure, diastolic blood pressure in men only, triglycerides, fasting plasma glucose in women only, insulin, proinsulin, and homeostasis model assessment of insulin resistance and was inversely associated with high-density lipoprotein (all P values <0.01). Similar results were observed in models that adjusted for both VAT and BMI. In a secondary analysis of incident CVD as an outcome, there was no statistically significant association observed for neck circumference in multivariable-adjusted models.
Conclusions: Neck circumference is associated with CVD risk factors even after adjustment for VAT and BMI. These findings suggest that upper-body sc fat may be a unique, pathogenic fat depot.
Visceral adipose tissue (VAT) is recognized as a unique, pathogenic fat depot, conferring metabolic risk above and beyond standard anthropometric measures, such as body mass index (BMI) and waist circumference (1). Individuals with large amounts of visceral fat are at increased risk of insulin resistance, type 2 diabetes, and atherosclerosis (24). However, VAT accounts for only modest correlations between cardiometabolic risk factors, suggesting that other mechanisms, or other fat depots, may also contribute to the development of cardiovascular disease (CVD) risk factors (1).
Upper body sc fat, as estimated by neck circumference, may confer risk above and beyond visceral abdominal fat. Anatomically, upper-body sc fat is a unique fat depot located in a separate compartment compared with VAT. Systemic free fatty acid concentrations are primarily determined by upper-body sc fat, suggesting that this fat depot may play an important role in risk factor pathogenesis (5). Elevated free fatty acid concentrations have been associated with insulin resistance, increased very-low-density lipoprotein cholesterol production, and endothelial cell dysfunction (6). Some studies have indicated that neck circumference may be an independent correlate of metabolic risk factors above and beyond BMI and waist circumference (710). In addition, a small study of men demonstrated that higher levels of upper-body sc fat, as measured by magnetic resonance imaging, were associated with higher low-density lipoprotein (LDL) and lower high-density lipoprotein (HDL) cholesterol levels (11). However, studies examining the joint impact of neck circumference and VAT have not as yet been reported.
Thus, the goal of this analysis is to characterize the cardiometabolic correlates of neck circumference and to ask the specific question of whether neck circumference is associated with cardiometabolic risk factors independently of VAT.

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