Hard arteries, weak bones

Abstract

Given the close association between bone and blood, it is not that surprising how the two common diseases of artery and bone, namely atherosclerosis and osteoporosis, may in part share a common pathogenesis. Although atherosclerosis and osteoporosis are both clearly more prevalent in later years, there is nonetheless increasing evidence of a bone-vascular connect independently linking osteoporosis with atherosclerosis beyond the occurrence of shared risk factors such as age, gender, smoking, lifestyle factors, alcohol, and diabetes. Several studies have shown how atherosclerosis is more common in both men and women with osteoporosis or low bone mass (‘osteopenia’). Regarding cerebrovascular disease, a study of over 9,500 women aged more than 65 years, showed how low areal bone mineral density (BMDa) at baseline increased the relative risk of stroke by 1.7 with low BMDa at baseline proving to be an even stronger predictor of subsequent stroke than systolic blood pressure [1]. In over 4,300 middle-aged to elderly men and women followed-up for an average 5.6 years, relative risk of both stroke and death from any cause was almost twice as high in those with osteoporosis at baseline even after adjusting for confounding variables such as age, smoking, diabetes, and hypertension [2]. In post-menopausal women, the decrease in lumbar BMDa is associated with an increase in carotid intimal thickness (p<0.01) [3]. Regarding cardiovascular disease, low BMDa independently predicts coronary artery disease in women undergoing coronary angiography better than traditional risk factors such as age, hypertension, diabetes, smoking, family history, or dyslipidemia [4]. In a study of over 2,500 postmenopausal women followed-up for more than 4 years, not only did women with osteoporosis have a 3.9-fold increased risk for cardiovascular events compared to women with low bone mass, it was also seen that the more severe the impairment of bone strength, as evidenced by the frequency and severity of vertebral fracture, the greater the risk of a subsequent cardiovascular event [5]. For peripheral vascular disease, a study of almost 6,000 elderly male subjects, followed-up for more than 5 years, showed how BMD loss was almost twice as pronounced in those with peripheral arterial disease as those with no peripheral arterial disease while the relative risk of nonspinal fracture was also increased by 1.47 [6]. Although low-energy fractures are a more reliable indicator of osteoporosis than BMD, when addressing the link between osteoporosis and atherosclerosis, BMD or other structural bone parameters may be more apt as vascular disease per se will increase the risk of fall and thereby the likelihood of fracture. Osteoporosis is linked to atherosclerosis and probably even more so to the occurrence of vascular calcification, which is a very frequent accompaniment of atherosclerosis. For example, in both sexes, lower lumbar vertebral trabecular BMD is more strongly associated with increasing calcification and severity of carotid atherosclerotic plaque J. F. Griffith (*) Department of Imaging and Interventional Radiology, The Chinese University of Hong Kong, Shatin, Hong Kong e-mail: griffith@cuhk.edu.hk