Abdominal Aortic Calcification Identified on Lateral Spine Images From Bone Densitometers Are a Marker of Generalized Atherosclerosis in Elderly Women

Abstract

Objective— Dual-energy x-ray absorptiometry is a low-cost, minimal radiation technique used to improve fracture prediction. Dual-energy x-ray absorptiometry machines can also capture single-energy lateral spine images, and abdominal aortic calcification (AAC) is commonly seen on these images. Approach and Results— We investigated whether dual-energy x-ray absorptiometry–derived measures of AAC were related to an established test of generalized atherosclerosis in 892 elderly white women aged >70 years with images captured during bone density testing in 1998/1999 and B-mode carotid ultrasound in 2001. AAC scores were calculated using a validated 24-point scale into low (AAC24 score, 0 or 1), moderate (AAC24 scores, 2–5), and severe AAC (AAC24 scores, >5) seen in 45%, 36%, and 19%, respectively. AAC24 scores were correlated with mean and maximum common carotid artery intimal medial thickness ( r s =0.12, P <0.001 and r s =0.14, P <0.001). Compared with individuals with low AAC, those with moderate or severe calcification were more likely to have carotid atherosclerotic plaque (adjusted prevalence ratio (PR), 1.35; 95% confidence interval, 1.14–1.61; P <0.001 and prevalence ratio, 1.94; 95% confidence interval, 1.65–2.32; P <0.001, respectively) and moderate carotid stenosis (adjusted prevalence ratio, 2.22; 95% confidence interval, 1.39–3.54; P =0.001 and adjusted prevalence ratio, 4.82; 95% confidence interval, 3.09–7.050; P <0.001, respectively). The addition of AAC24 scores to traditional risk factors improved identification of women with carotid atherosclerosis as quantified by C -statistic (+0.075, P <0.001), net reclassification (0.249, P <0.001), and integrated discrimination (0.065, P <0.001). Conclusions— AAC identified on images from a dual-energy x-ray absorptiometry machine were strongly related to carotid ultrasound measures of atherosclerosis. This low-cost, minimal radiation technique used widely for osteoporosis screening is a promising marker of generalized extracoronary atherosclerosis.