Bone disease: the link with stroke.

Older women with the bone disease osteoporosis have always has to worry about breaking a hip. A new study indicates that such women also face an increased threat of stroke.

A stroke occurs when the blood supply to part of the brain becomes insufficient, thus damaging or killing nerve cells. A 1991 study had hinted at a link between stroke and osteoporosis, a disorder in which bones lose tissue mass and become fragile and more subject to fractures.

To confirm that surprising association, Warren S. Browner at the University of California, San Francisco, and his colleagues studied 4,024 women age 65 and older. The team measured bone density at the start of the study and then monitored the women for two years. During that period, 83 of the women suffered a stroke.

A statistical analysis revealed an association between low bone density and an increased risk of stroke. Indeed, the connection was as strong as the well-established link between high blood pressure and stroke.

It is well known that there is a cause-effect relationship between high blood pressure and stroke. Elevated pressures can damage the artery wall and thus trigger the formation of a stroke-causing blood clot or a rupture in the vessel itself.

However, Browner and his colleagues believe bone density and stroke are linked in a different way.

"We don't think osteoporosis causes strokes," he says. Instead, the team suspects a common condition, such as decreased estrogen production after menapause, may lead to both osteoporosis and stroke.