WHAT IS OSTEOPOROSIS?

Osteoporosis, which literally means porous bone, is a disease in which the density and quality of bone are reduced. As bones become more porous and fragile, the risk of fracture is greatly increased. The loss of bone occurs silently and progressively. Often there are no symptoms until the first fracture occurs.

What causes osteoporosis?

Left: normal bone, right: osteoporotic bone

Our bones are living tissue and constantly changing. From the moment of birth until young adulthood, bones are developing and strengthening. Our bones are at their most dense in our early 20s – called peak bone mass. 

As we age some of our bone cells begin to dissolve bone matrix (resorption), while new bone cells deposit osteoid (formation). This process is known as remodeling.

For people with osteoporosis, bone loss outpaces the growth of new bone. Bones become porous, brittle and prone to fracture. 

Osteoporotic fractures

Around the world, 1 in 3 women and 1 in 5 men aged fifty years and over are at risk of an osteoporotic fracture. In fact, an osteoporotic fracture is estimated to occur every 3 seconds. The most common fractures associated with osteoporosis occur at the hip, spine and wrist. The likelihood of these fractures occurring, particularly at the hip and spine, increases with age in both women and men.

PREVENTING OSTEOPOROSIS

Genetic factors play a significant role in determining whether an individual is at heightened risk of osteoporosis. However, lifestyle factors such as diet and physical activity also influence bone development in youth and the rate of bone loss later in life.

After your mid-20s, bone thinning is a natural process and cannot be completely stopped. The thicker your bones, the less likely they are to become thin enough to break. Young women in particular need to be aware of their osteoporosis risk and take steps to slow its progress and prevent fractures.

Children and adolescents should:

• Ensure a nutritious diet with adequate calcium intake 
• Avoid protein malnutrition and under-nutrition
• Maintain an adequate supply of vitamin D
• Participate in regular physical activity
• Avoid the effects of second-hand smoking
•  

It’s estimated a 10% increase of peak bone mass in children reduces the risk of an osteoporotic fracture during adult life by 50%.

Adulthood

Bone mass acquired during youth is an important determinant of the risk of osteoporotic fracture during later life. The higher the peak bone mass, the lower the risk of osteoporosis.

Once peak bone mass has been reached, it is maintained by a process called remodeling. This is a continuous process in which old bone is removed (resorption) and new bone is created (formation). The renewal of bone is responsible for bone strength throughout life.

During childhood and the beginning of adulthood, bone formation is more important than bone resorption. Later in life, however, the rate of bone resorption is greater than the rate of bone formation and results in net bone loss –a thinning of your bones.

Adults should:

• Ensure a nutritious diet and adequate calcium intake 
• Avoid under-nutrition, particularly the effects of severe weight-loss diets and eating disorders
• Maintain an adequate supply of vitamin D
• Participate in regular weight-bearing activity
• Avoid smoking and second-hand smoking
• Avoid heavy drinking

DIAGNOSING OSTEOPOROSIS

Men and women over 60-years-old are at higher risk of osteoporosis than younger people. Nevertheless, it is possible to have osteopenia (low bone mass) or osteoporosis at a much earlier age. As osteoporosis has no obvious symptoms, it's important to go to your doctor if any risk factors apply to you.

By making positive lifestyle changes and following appropriate treatment strategies in consultation with a doctor, osteoporotic fractures can be prevented. Your doctor will take a thorough medical history that includes information on any recent fractures and may determine the next step is to have a bone mineral density (BMD) test. 

What is a BMD test?

Traditional X-rays can’t measure bone density, but they can identify spine fractures. Bone mineral density (BMD) has to be measured by more specialized techniques. A number of different types of BMD tests are available, but the most commonly used is DXA (dual-energy X-ray absorptiometry)

DXA is a low radiation X-ray capable of detecting quite small percentages of bone loss. It is used to measure spine and hip bone density, and can also measure bone density of the whole skeleton. 

What do my test results mean?

The World Health Organization has defined a number of threshold values (measurements) for osteoporosis. The reference measurement is derived from bone density measurements in a population of healthy young adults (called a T-score). Osteoporosis is diagnosed when a person’s BMD is equal to or more than 2.5 standard deviations below this reference measurement 

Osteopenia is diagnosed when the measurement is between 1 and 2.5 standard deviations below the young adult reference measurement.

If the results of your BMD test show osteopenia or osteoporosis, it does not automatically mean that you will have a fracture. There are lifestyle changes and a number of available therapies that your doctor might prescribe to slow down bone loss and help prevent fractures.

References:

1. World Health Organization. Assessment of fracture risk and its implication to screening for postmenopausal osteoporosis: Technical report series 843. Geneva: WHO,1994

2. Kanis J. Diagnosis of osteoporosis and assessment of fracture risk. Lancet 2002;359:1929-36

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