Decreasing bone mineral density (BMD) leads to arterial stiffening and calcification and may be an independent risk factor for cardiovascular disease, report researchers in the UK.
Michelle Frost (Guy's Hospital, London, UK) and co-workers note that "osteoporosis and cardiovascular disease have traditionally been viewed as two separate diseases that increase in incidence with age and, therefore, frequently co-exist."
However, they add: "Recent evidence suggests that age-independent associations exist between BMD and cardiovascular disease risk."
To investigate further, Frost and team measured BMD, arterial stiffness, and arterial calcification in 54 postmenopausal women. Arterial stiffness was assessed by pulse wave velocity testing, while calcification and BMD were measured by ultrasonography and dual X-ray absorptiometry, respectively.
This analysis revealed that 59% of the participants who had osteoporosis also had calcified plaques in at least one area. This was a greater plaque burden than that seen in women with osteopenia or normal BMD, in whom plaques were found in 42% and 20%, respectively.
Furthermore, the authors were able to establish significant negative links between arterial stiffness and BMD at the hip that were independent of traditional risk factors for increased arterial stiffness including age, arterial blood pressure, and lipid levels.
Arterial stiffness was also significantly correlated with levels of the osteoclastogenesis inhibitor osteoprotegerin, a relationship which was independent of age, the authors write in the journal Calcified Tissue International.
The researchers note, however, that osteoprotegerin levels were not significantly related to BMD.
Attempting to explain their findings, the authors note that it was once believed that calcium lost from bone was absorbed directly by vascular tissues, thereby leading to calcification of those tissues.
This is unlikely, they say, since serum calcium and phosphate levels are rigidly regulated by the body.
Regardless of the mechanism involved, the authors conclude that their findings "support the hypothesis that increased cardiovascular disease risk in women with decreased BMD is associated with arterial calcification and raise the possibility that osteoprotegerin is a sensitive marker of arterial stiffening, independent of any association with BMD."