Low bone mineral density (BMD) is associated with obstructive coronary artery disease (CAD); this article reviews several recent studies that have demonstrated the association. In one study, for every 1-unit reduction in femoral neck T score, a 0.23 minute decrease in treadmill exercise duration was found after values were adjusted for age and other patient characteristics (95% confidence interval [CI], 0.11–0.35, p<0.001). For every 1-unit reduction in femoral neck T score, there was a 22% increased risk of myocardial ischemia after values were adjusted for age and other patient characteristics (95% CI, 1.06–1.41, p = 0.004). Overall after adjustments, patients with a low BMD who were referred for exercise echocardiographic stress testing had a 43% greater risk of myocardial ischemia than did patients with normal BMD referred for exercise echocardiographic stress testing (95% CI, 1.06–1.94, p = 0.02). Reduced physical activity may contribute to both low BMD and CAD through the development of atherosclerotic vascular disease.
In a second study, stress test-induced myocardial ischemia developed in 95 of 254 patients (37%) with osteoporosis, in 81 of 260 patients (31%) with osteopenia, and in 62 of 251 patients (25%) with normal BMD (p= 0.009) (p= 0.002 comparing osteoporosis with normal BMD; p=0.007 comparing osteoporosis or osteopenia with normal BMD). Patients with osteoporosis or osteopenia had a 1.7 times higher chance of stress test-induced myocardial ischemia than those with normal BMD after controlling the confounding effects of systemic hypertension, diabetes mellitus, body mass index, and age.
Key words: osteoporosis, osteopenia, bone mineral density, coronary artery disease, myocardial ischemia.
Shechar Dworski, BSc
Osteopenia literally means "poverty of bone," while osteoporosis (OP) means "porous bone." The underlying cause of both conditions is a difference in the rate of bone formation and bone loss. Normally, both processes take place at equal rates resulting in a dynamic equilibrium. Bone density peaks during the second or third decade of life and then gradually declines with age, when bone loss exceeds bone formation. Bone is formed in response to physical stresses imposed on it, so excessive loss may occur as a result of immobility. Other causes of excessive loss include hormonal changes, either after menopause, or with excess parathyroid or corticosteroid hormones, or insufficient vitamin D or calcium intake.
In radiological terms, osteopenia refers to an increased radiolucency of bone. The most common cause of this is OP, although there are other causes for osteopenia, such as osteomalacia (so-called "renal rickets", Vitamin D deficiency-related problems), hyperparathyroidism, and some renal diseases. Renal osteodystrophy (or uremic bone disease) is the term for a complex group of bone disorders that occur in patients with chronic renal failure (CRF). Specific radiographic clues for other causes of osteopenia include: looser zones found in osteomalacia, subperiosteal resorption present in hyperparathyroidism, and focal lytic lesions (as seen in disseminated multiple myeloma).
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