What is it?
- The term osteoporosis has been defined as "a decrease in bone mass and architectural deterioration of bone tissue, leading to enhanced bone fragility and consequent increase in fracture risk"
- Bones that were once strong enough to support our body (Fig. 1 below) become fragile and fracture more easily (Fig. 2 below)
- The main causes of osteoporosis are hormonal imbalance (oestrogen and testosterone) and long-term use of corticosteroids that result in an imbalance in the continual process of old bone tissue being replaced by new, termed remodelling, that occurs at the bone-marrow interface.
- During remodelling, osteoclast cells resorb bone and osteoblast cells form new bone; in osteoporosis, there is generally both increased bone resorption and decreased bone formation.
- Most pharmaceutical agents prescribed for osteoporosis are aimed at preventing further bone loss (anti-resporptives, e.g. oestrogen, bisphosphonates) although new agents have recently been approved that add bone (e.g. parathyroid hormone and strontium ranelate).
- The cost to Australia of osteoporotic fractures in subjects aged over 60 years of age was estimated in 1996 to be $779 million. With an ageing population the problem will grow dramatically unless successful strategies for preventing and treating osteoporosis are devised. Within Australia, it has been estimated that after the age of 60 years about 60% of women and 30% of men suffer from an osteoporotic fracture. Mortality after hip fracture is 24% at 12 months, about five times higher than in an age-matched group who do not suffer a hip fracture. 26% of people with hip fractures remain in nursing homes for the rest of their lives and 50% never regain their pre-fracture independence. In 1994 there were 14,600 hip fractures in Australia, it is estimated that this figure will rise to 20,900 by 2010.
- Screening for osteoporosis has not been advocated to date due to a) the insufficient fracture prediction capability of conventional bone mineral density assessment and b) the low efficacy of available treatments. This project is significant to both of these issues, since it has the potential to enable us a) to better predict future bone loss and hence future fracture risk, and b) to better predict response to treatment and hence efficacy on an individual subject basis.