Osteoporosis

By Associate Professor Nicholas Pocock MD, FRACP, St Vincent's Hospital, Sydney Biographical note

Introduction

Osteoporosis is a common disease of old age, which results in a decrease in the amount of bone in the skeleton, as well as a deterioration in the bone structure. These changes result in a weakening of the skeleton, leading to an increased chance of breaking a bone; a fracture. The most common sites of fracture are the bones of the spine, the hip and the wrist. However other bones are commonly affected, including the shoulder (proximal humerus), ribs and the pelvis. Osteoporosis is most common in women after menopause but elderly men are also commonly affected.

Osteoporosis is often called a silent disease because it doesn t cause any symptoms until a bone is broken. The pain of osteoporosis may last 4 to 6 weeks as the bone heals, but in most cases the pain gradually disappears. In the spine, however, some patients experience long term pain after a fracture, due to alteration in the mechanics of the back. At most sites in the skeleton, when an osteoporotic bone breaks it is easily identified and the diagnosis of osteoporosis can be made. In the spine, however, a fracture of a vertebra may be missed. This means that in any middle aged or elderly person, any back pain should be viewed suspiciously in case it indicates a fracture. In addition, sometimes a fracture of an osteoporotic bone in the spine may not cause any symptoms at all. Once a person has one osteoporotic fracture they are at a high risk of having further, perhaps more serious, fractures.

Cause of Osteoporosis

There is no one cause of osteoporosis. Many factors contribute to a loss of bone as people age. In women, the decrease in the level of sex hormones (oestrogens) after the menopause is an important cause of bone loss. Other factors however are also important including genetic make-up and a number of lifestyle factors such as diet, exercise levels and smoking. Low body weight, generally considered below 58kg, or significant loss of weight as people age, are also important factors which increase the risk of developing osteoporosis. A number of diseases also increase the risk of developing osteoporosis such as rheumatoid arthritis, coeliac disease and chronic lung diseases. Certain medications, particularly cortisone or prednisone may also result in increased loss of bone.

Osteoporosis Prevalence in Australia and Overseas

It is estimated that in Australia approximately 60% of women, and 30% of men, over the age of 60 years will suffer an osteoporotic fracture in their remaining lifetime (1). In Australia osteoporosis already poses a major public health problem and was responsible for more than 15,000 hip fractures alone in 1996 (2). At present the cost of all of these fractures in Australia exceeds $1.9 billion per year (3). It is estimated that in Australia by the year 2025, these fractures will more than double and hip fractures alone will exceed 32,000 per annum (2). Overseas osteoporosis is a major health care problem in most countries and is predicted to increase markedly in the next two decades due to the expected aging of the population. In the USA for example, the figures are correspondingly higher than in Australia and the annual cost of osteoporosis related fractures in that country exceeds $US14 billion (4).

The Diagnosis of Osteoporosis

In the past the diagnosis of osteoporosis often was not made until late in the disease when a fracture occurred or there were obvious changes on X-rays. Standard X-rays however are not very sensitive at diagnosing osteoporosis and usually won t detect the disease until 30% or more of the bone tissue has been lost. Fortunately a more sophisticated X-ray technique, called Dual Energy X-ray Absorptiometry (DXA) is now available. This safe and painless technique is also often referred to as bone densitometry and allows the early diagnosis of osteoporosis before a fracture has occurred. Bone densitometry is now readily available in Australia and in some cases the costs are reimbursed by Medicare.

Prevention of Osteoporosis

A number of general dietary and life style measures can decrease the risk of osteoporosis, but while important do not guarantee that osteoporosis will not develop. These life style measures include:

- Exercise: Weight bearing exercise helps reduce bone loss, as well as maintain muscle strength and reflexes. Regular exercise such as walking, jogging, playing tennis or aerobic classes are recommended to help in prevention of osteoporosis.
- Nutrition: Inadequate calcium in the diet increases the risk of developing osteoporosis. At all ages it is important to obtain adequate levels of Calcium in the diet. The recommended calcium intake for adults is 800 - 1,000 mg/day and for postmenopausal women and elderly men 1000 - 1500 mg/day. The main source of calcium is from dairy products but calcium supplements are also a good source for individuals who don't consume milk or other dairy products.
- Tobacco and alcohol use: Smoking and heavy alcohol use, increase the risk of developing osteoporosis. It is recommended that alcohol intake be limited to no more than two standard alcoholic drinks per day. Patients should also be encouraged to stop smoking which is an important cause of increasing the risk of an osteoporotic fracture.
- Vitamin D: Vitamin D deficiency, which increases the risk of fracture, becomes more common with increasing age, particularly in individuals who receive limited sun exposure such as nursing home residents. The main source of vitamin D is sunlight acting on the skin, but it is also found in some foods. It is important to ensure adequate Vitamin D particularly as people age. Vitamin D preparations are often useful in supplementing the natural sources of Vitamin D.

Treatment of Osteoporosis

Previously there was a widespread belief that there was not much that could be done for osteoporosis, which many people, including some doctors, considered an inevitable consequence of aging. Recently however a number of new medications have been developed and in the last few years these have been shown to be effective in restoring lost bone and can decrease the risk of an osteoporotic fracture by approximately 50%. Other new drugs are also currently being investigated which potentially may be even more effective in the treatment of osteoporosis.

In addition to measures to maintain the strength of our bones, it is also important to minimise the risk of falls, which may result in a fracture. Thus other measures such as sensible foot-ware, avoidance of slippery surfaces and correction of impaired vision when possible, are also important in decreasing the risk of an osteoporotic fracture.

Some medications, particularly sedatives and some blood pressure tablets, may also increase the risk of falling and this should be considered in the use of these medicines in the elderly. Simple measures around the home such as the removal of loose rugs, or better lighting in dark areas, are also helpful in reducing falls. Many community health care providers have active fall prevention programmes which provide useful advise and assistance in helping prevent or reduce the number of falls in the elderly.

Osteoporosis Mortality and Quality of Life (5)

Most osteoporotic fractures, while causing significant disability, do not result in death. Osteoporotic hip fractures however may be very serious and often result in surgery to stabilise the fracture. Of the individuals who fracture a hip, half will be permanently disabled and never regain their former independence, and 20-25% will require long-term nursing care. Approximately 12-15% of hip fracture patients die within 6 months of the injury, as a consequence of the fracture and its complications, or as a result of subsequent immobility. While fractures at sites apart from the hip don t usually result in the death of the patients, they nevertheless do cause much disability and hardship.

References

Jones G, Nguyen T, Sambrook PN et al Symptomatic fracture incidence in elderly men and women: the Dubbo Osteoporosis Epidemiology Study (DOES). Osteoporosis Int 1994; 4:277-282.
Health burden of hip and other fractures in Australia beyond 2000. Projections based on the Geelong Osteoporosis Study. Sanders KM, Nicholson GC, Ugoni AM et al. MJA 1999; 170: 467-470
The Burden of Brittle Bones in Australia: Costing Osteoporosis in Australia. Prepared by Access Economics, Canberra ACT, September 2001. Commissioned by Osteoporosis Australia.
Ray NF, Chan JK, Thamer M, Melton LJ. Medical expenditures for the treatment of osteoporotic fractures in the United States in 1995; report from the National Osteoporosis Foundation. J Bone Miner Res 1997;12:24-35.
March L, Chamberlain A, Cameron I et. al. Prevention, treatment and rehabilitation of fractured neck of femur. Health Outcomes Project 1996. Public Health Unit, Northern Sydney Area Health Service.

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Reviewed March 2007

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