Bone density tests measure the strength of your bones. They help determine your risk for sustaining a bone fracture. Let’s consider when you might need a bone density test and when you don’t.
Bone is a highly dynamic tissue that is constantly undergoing remodeling with bone resorption and bone formation occurring simultaneously. Peak bone mass is usually achieved by the age of 30. After that age, the amount of new bone formation decreases while the bone resorption remains the same resulting in a net loss of bone density.
Although all people experience some amount of bone loss as they grow older, which is called osteopenia, the rate of bone loss is generally mild and they are not at high risk for sustaining fractures. They will not need bone testing and can preserve enough bone mass for routine activities by exercising regularly and ensuring adequate intake of calcium and vitamin D.
What a Bone Density Test Can Do
A bone density test tells you if you have normal bone density, low bone density, or osteoporosis. It is the only test that can diagnose osteoporosis. The lower your bone density, the greater your risk of breaking a bone. A bone density test can help you and your healthcare provider:
- Learn if you have weak bones or osteoporosis before you break a bone
- Predict your chance of breaking a bone in the future
- See if your bone density is improving, getting worse or staying the same
- Find out how well osteoporosis medicine is working
- Let you know if you have osteoporosis after you break a bone
Who Should Have a Bone Density Test
In some people, the decrease of bone density occurs to the point of potential fracture. Indications for bone density tests:
- Women over the age of 65 because of the change in hormone levels after menopause make their bones weaker
- Men over the age of 70
- Smokers and heavy drinkers as these activities cause leaching of calcium from bones
- Having a low body weight which might indicate a low of bone mass
- Use of corticosteroids for greater than 3 months as this might affect hormone levels
- Sustaining a hip fracture from a low energy fall or breaking a bone as a result of a minor accident which might indicate osteoporosis (abnormally increased in the porosity of bone)
How Often to Repeat a Bone Density Test
People taking an osteoporosis medicine should repeat their bone density test by central DXA every one-two years. After starting a new osteoporosis medicine, many healthcare providers will repeat a bone density test after one year.
Understanding Bone Density Test Results
Your bone density test results are reported using T-scores. A T-score shows how much your bone density is higher or lower than the bone density of a healthy 30-year old adult. A healthcare provider looks at the lowest T-score to diagnosis osteoporosis.
What Your T-score Means. According to the World Health Organization (WHO):
- A T-score of -1.0 or above is normal bone density. Examples are 0.9, 0 and -0.9.
- A T-score between -1.0 and -2.5 means you have low bone density or osteopenia. Examples are T-scores of -1.1, -1.6 and -2.4.
- A T-score of -2.5 or below is a diagnosis of osteoporosis. Examples are T-scores of -2.6, -3.3 and -3.9.
- The lower a person’s T-score, the lower the bone density. A T-score of -1.0 is lower than a T-score of 0.5 and a T-score of -3.5 is lower than a T-score of -3.0.
Your bone density test result also includes a Z-score that compares your bone density to what is normal in someone your age and body size. Among older adults low bone mineral density is common, so Z-scores can be misleading.
When to Consider Treatment
The results of a bone density test help your healthcare provider make recommendations about what you can do to reduce your chance of breaking a bone. When making a decision about treatment with an osteoporosis medicine, your healthcare provider will also consider your risk factors for osteoporosis, your likelihood of breaking a bone in the future, your medical history and your current health.
Below are treatment guidelines for postmenopausal women and men age 50 or older:
- Most people with T-scores of -1.0 and above (normal bone density) do not need to take an osteoporosis medicine.
- Some people with T-scores between -1.0 and -2.5 (low bone density or osteopenia) should consider taking an osteoporosis medicine when they have certain risk factors.
- All people with T-scores of -2.5 and below (osteoporosis) should consider taking an osteoporosis medicine.