It is estimated that the proportion of women with osteoporosis (low bone mineral density) increases from 15% in those aged 60 to 64 years up to 71% in those over 80 years of age. The incidence is much lower in men, ranging from 1.6% of those aged 60 to 64 years up to 19% of those aged over 80 years.

The epidemiology of fractures differs considerably from country to country. The reasons for the difference are unknown, but variable surveillance and problems with ascertainment bias may contribute. Most of the studies on osteoporosis relate to white women, and there are limited data on osteoporosis in men. There are few data on the epidemiology of osteoporosis in Australia. No separate information appears to be available for Aboriginal or Torres Strait Islander people, or for specific ethnic groups. The Dubbo Osteoporosis Epidemiology Study involved a large cohort of elderly men and women studied prospectively from 1989 onwards. Its findings indicate that after the age of 60 years about 60% of women and 30% of men suffer from an osteoporotic fracture. Direct costs associated with osteoporotic fractures were assessed, and the total annual cost for Australia was estimated to be $779,000,000 (in 1992 Australian dollars). Rehabilitation comprised the largest proportion of costs for hospital-treated fractures, and community services were the largest cost for outpatient-treated fractures. These estimates do not include the personal costs of loss of independence and mobility.

There is more information available about hip fractures than any other fracture type, because virtually all patients with hip fracture are hospitalised. Vertebral fractures, in particular, are not always symptomatic, and it is therefore not possible to define their true incidence. In the Dubbo Osteoporosis Epidemiology Study only 10% of fractures in people aged 60 to 79 years were hip fractures, compared with 40% in those aged over 80 years. In a recent study conducted in the northern Sydney area, mortality after hip fracture was 24% at 12 months, about five times higher than that in an age-matched group who did not suffer a hip fracture. Between 20% and 26% of people with hip fractures remain in nursing homes for the rest of their lives. Numerous studies in the United States, Europe and Australia have found that around 50% of people who suffer a hip fracture never regain their prefracture mobility.

The problem of osteoporotic fractures is already large and is increasing with the ageing of the population. In 1994, there were 14,600 hip fractures in Australia. If nothing is done to reduce risks, it is estimated that in 2010 there will be 20,900 hip fractures in Australia.

Next: What is the relationship between bone density and fracture risk; are there any other useful predictors of fracture risk?