Impact of central obesity on the estimation of carotid-femoral pulse wave velocity

Abstract

Background: Studies have found that central obesity is associated with higher carotid-femoral pulse wave velocity (PWV). However, traveled distance (TD) measured over the body surface can be substantially overestimated with wider waist circumference (WC). We sought to investigate whether central obesity biases the estimation of PWV and whether this bias explains the association between PWV and different measures of adiposity.

Methods: Seven hundred eleven participants (49.5% men) from the Baltimore Longitudinal Study of Aging with PWV, anthropometrics, and quantification of different fat depots by computed tomography and dual x-ray absorptiometry were included. TD and relative PWV were estimated with a tape measure over the body surface or linear distances taken from radiological images, unaffected by obesity.

Results: A significant association was found between wider WC and a greater difference between the 2 TD measurements and their respective PWV in both sexes (r ≥ 0.34; P < 0.001). This overestimation bias appeared to be generally higher in women than men (0.27 m/sec for each unit increase in WC; P < 0.0001). When TD estimated over the body surface was used to calculate PWV, greater WC, total body fat, subcutaneous fat, and visceral fat were all associated with higher PWV (P < 0.05 for all). However, when PWV was calculated using TD estimated from radiological images or body height, only the association with visceral fat held significant.

Conclusions: When TD is measured over the body surface, the role of obesity on PWV is substantially overestimated. After accounting for this bias, PWV was still independently associated with visceral fat but not with other measures of adiposity, confirming its contribution to arterial stiffening.

Keywords: arterial stiffness; blood pressure; hypertension; obesity; pulse wave velocity; travel distance; visceral fat; waist circumference..

Figure 1.

Estimation of carotid–femoral traveled distance over the body surface and using computed tomography (CT) scout images. (a) Carotid–femoral distance was estimated over the body surface using a tape measure and (b) on CT scout images using the ImageJ software and according to a specific protocol (see text for details). In the formula in b, L4_FN was calculated as the square root of the sum of the squares of L4_PS and FN_PS; CA_MS was the same measured above the body surface because this measure is not affected by central obesity. The arrowed line in a represents graphically the potential impact of central obesity in overestimating distances taken over the surface of the body. Abbreviations: CA, carotid artery; FA, femoral artery; L4, fourth lumbar vertebra; FN, femoral neck; MS, manubrium of the sternum; PS, pubic symphysis; UMB, umbilicus.

Figure 2.

Relationship between waist circumference and the difference in body-derived minus computed tomography (CT)–derived traveled distance and pulse wave velocity. (a) The difference in traveled distance (TD) for women (circles, dashed lines) and men (dots, solid lines) was calculated subtracting the TD calculated from CT scout images from the TD measured over the body surface with a tape measure. (b) The respective pulse wave velocity values were calculated, subtracted, and plotted against waist circumference.