This is the third in a series of columns, exclusive to HealthandBone.ca that will focus on issues that are important to you, as a person concerned about their own bone health, or of that of a family member or friend. Dr. Marla Shapiro will draw upon her expertise and that of other expert colleagues to keep you up-to-date on the latest thinking in osteoporosis.
As I discussed in my first column on health and bone, although it may seem as though it snuck up on you, osteoporosis is not something that develops overnight. Osteoporosis is a long-term disease – the result of low bone mass and the breakdown of bone over time. The first sign that there is any problem at all may very well be a bone break or fracture. Osteoporosis steals valuable bone mass and corrodes bone tissue, without you even knowing it, leaving your bones weak and vulnerable to a break.
Detecting osteoporosis early is important and can help prevent fractures from occurring in the first place. Having your bone mineral density (BMD) tested will help your doctor determine whether you are at risk or whether or not you have low bone mass or osteoporosis.
A BMD test is safe and painless. It involves lying on a table for about 10 to 20 minutes while low x-ray radiation is used to measure the thickness of your bones. Small amounts of x-ray radiation are transmitted through your bones. The amount passing through is measured. A particular kind of doctor called a radiologist can determine how thick or thin (dense) your bones are by measuring the amount of light passing through them. The more light passing through, the less dense your bones are.
BMD test results are given to you in the form of a number called a T-score. How is this number calculated? When you have your bone mineral density tested, it is compared to an established standard. The T-score represents this comparison. T-scores tell you how far your bone mineral density differs or deviates from what is considered to be normal for a young adult.
According to the World Health Organization, a T-score between +2.5 and -1 is considered normal; a T-score between -1 and -2.5 is considered low bone mineral density (osteopenia) and a T-score below -2.5 indicates osteoporosis.
BMD testing is an important diagnostic tool but it is only part of the equation in determining fracture risk.
While BMD is important, doctors are likely to look at other factors as well to determine what is referred to as absolute 10-year fracture risk. This is your likelihood of having a hip or major osteoporosis-related fracture within the next 10 years.
There are four key factors that can increase your risk for fracture.
|Risk factors for fracturing|
Using your BMD and age and taking into consideration any of the risk factors you may have from the table above can help your doctor determine your absolute 10-year fracture risk.
Adapted from Siminoski 2005, p. 182.
This table represents your fracture risk taking into account age and BMD T-score. For example, if you are a 65 years old woman and your BMD T-score is -2.0, you are at moderate risk of fracture. However, your fracture risk goes up one level (from low to moderate or, in this case, from moderate to high) if you have had a fracture or are taking steroids such as prednisone. If you have both of these risk factors, then you are at high risk no matter what your T-score is
Knowing your 10-year absolute fracture risk is helpful for your doctor in determining what is the best way to manage your osteoporosis. Based on your fracture risk he or she may recommend any or all of the following, depending on what your risk is: