Why is the IAEA collecting global data on osteoporosis?

• Osteoporosis is a disorder that reduces both the amount and strength of bone tissue making bones more susceptible to fracture. It is one of the most common age afflictions and presents a major public health problem. As many as 200 million people may be affected.

• It severely limits quality of life and, as in the case of hip fractures, produces substantial disability.

• It is imposing a growing financial burden on the health-care systems in both developed and developing countries.

Causes of osteoporosis

Bone mineral mass in an individual is the result of a variety of factors including genetic factors, physical exercise, hormonal factors, but there is little doubt that nutrition plays a key role. Important dietary components include essential nutrients (calcium, phosphorus, vitamin D, vitamin C, magnesium, potassium, copper, manganese, fluorine and zinc). The most obvious deficiency in an osteoporotic patient is the calcium - the most important mineral constituent of the bone and the principal component of bone strength.

Sufficient dietary intake and absorption of calcium is important in the prevention and treatment of osteoporosis. But, calcium is not the only essential element. Recent evidence suggests that dietary supplementation with magnesium, copper, manganese, and zinc may also have a favourable impact on bone density.

There is a great need to understand more about:

• risk factors and prevention;

• global variations in incidence and severity between population groups; and

• diagnosis and prevention.

Risk factors of osteoporosis: conventional indicators and isotope techniques

Isotopic techniques are gaining prominence in studies of osteoporosis and related issues of bone metabolism.

Bone mass measurements

Measuring bone mass is essential to diagnosing and managing osteoporosis and potential bone fractures. In recent years, a number of non-invasive techniques have been introduced to quantify bone mass with high accuracy and precision, although standardization remains difficult. To obtain internationally comparative data the preferred technique for bone density measurements in the IAEA programme is DEXA (dual energy X-ray absorptiometry), a technique developed using a radioisotope source but now usually applied with an X-ray generator.

Study of elements in bone and diets

In addition, neutron activation analysis (in the laboratory) are suitable techniques for determining minerals and trace elements in foods, diets and human tissues including bone. This has already been demonstrated successfully in a number of IAEA research programmes. Other possibilities for applying isotopic and nuclear-related techniques in studies of osteoporosis and related issues of bone metabolism are shown in table below.

What is measured	Isotopic Method
Bone density Calcium metabolism (uptake and turnover) Whole- or partial body calcium Trace elements in bone and diet Energy expanditure, protein turnover Hormones related to bone metabolism, biochemical markers of bone formation	DEXA (Dual Energy X-ray Absorptiometry Stable/radioactive isotopes In vivo neutron activation analysis In vitro neutron activation analysis Stable isotope applications (doubly labelled water and 13C or 15N-tracer) Radioimmunoassays (RIA)

IAEA's role in preventing osteoporosis

Internationally comparative studies are shedding new light on the causes of this disease and will contribute to developing effective preventive strategies. IAEA is undertaking such studies of the incidence and severity of osteoporosis in predominately urban population groups in Canada, Brazil, Chile, Russia, China, the Philippines, Singapore, Hungary, Croatia, and Turkey. Using DEXA, the goal is to measure bone density for the purpose of:

• determining age of peak bone mass in each study group;

• investigating how bone mineral density varies with age, sex, ethnicity and geographical origin of the subjects; and

• assessing the role of trace elements in relation to bone metabolism, composition structure and development of bone disease.

Factors such as hormones, physical exercise, and protein metabolism which are related to development of osteoporosis and measurable by isotopic techniques are also being incorporated. In addition, dietary supplementation studies with minerals, trace elements and vitamins will be conducted over a 2-year period in each of the participating countries. The bone mineral density will be measured to detect any sequential changes.

The acquired data will be valuable in planning and developing preventive strategies for osteoporosis and reducing current health care cost. This is of importance as the disease is more readily prevented than treated, and early intervention with effective therapy would be expected to significantly reduce the impact of fracture among the aging population.