Older women with high bone density are about twice as likely to develop breast cancer, a new study has found.

These results add to existing evidence that suggests that older women who have low bone mass have a decreased risk of breast cancer and, conversely, that higher bone density is associated with increased risk of breast cancer.

Bone mineral density can be an accurate marker of the body's response to oestrogen, in that women with higher bone density are thought to be physiologically more sensitive to the hormone's effects than women with lower bone density.

Because oestrogens have also been …