What is a bone density test (DEXA scan)?
A bone density test, most commonly a Dual-energy X-ray Absorptiometry (DEXA or DXA) scan, is a non-invasive imaging procedure that measures the mineral content of your bones. It uses a very low dose of X-rays to create images, primarily of the hip and spine, which are key areas for assessing fracture risk. The test takes about 10–30 minutes to complete and is considered the most accurate method for measuring bone mineral density (BMD).
During a central DEXA scan, you lie on a padded table while a mechanical arm passes over your body. A computer then analyzes the images to determine your bone density and compare it to established norms. This comparison results in a T-score and/or a Z-score, which your doctor uses to interpret your bone health.
Interpreting your DEXA scan results: T-scores and Z-scores
After your DEXA scan, a radiologist interprets the images and a report is generated. The most important metric for postmenopausal women and men over 50 is the T-score.
- T-score of -1.0 or higher: This is considered normal bone density, indicating strong, healthy bones.
- T-score between -1.0 and -2.4: This indicates low bone density, also known as osteopenia. It means your bones are weaker than normal but not yet classified as osteoporosis.
- T-score of -2.5 or lower: This result indicates you have osteoporosis, a condition of very low bone density that significantly increases your fracture risk.
The Z-score is used for premenopausal women, younger men, and children. It compares your bone density to that of people of your same age, sex, weight, and ethnic origin. This can help doctors identify if an underlying medical condition, rather than aging, is contributing to low bone mass.
When to get tested for dense bones
While dense bones are generally a good thing, extremely high bone density can be a sign of rare genetic conditions like osteopetrosis, which paradoxically can lead to weaker, more brittle bones. However, for most people, the concern is low bone density (osteoporosis). Screening guidelines are in place to help identify those at risk. You should consider a DEXA scan if:
- You are a woman aged 65 or older.
- You are a man aged 70 or older.
- You are postmenopausal or an older man with specific risk factors.
- You have experienced a fracture after age 50.
- You have lost more than 1.5 inches of height.
- You have certain medical conditions or take medications known to cause bone loss.
Factors influencing bone density
Bone density is not solely determined by genetics; a combination of controllable and uncontrollable factors influence your bone health. It's important to understand these to take proactive steps.
| Factor | Impact on Bone Density | Controllable? | How to Manage |
|---|---|---|---|
| Age | Bone mass naturally decreases after peak mass is reached around age 30. | No | Proactive monitoring and lifestyle choices. |
| Genetics | Family history and inherited genetic variations can influence peak bone mass. | No | Be aware of your family history and inform your doctor. |
| Diet | Inadequate intake of calcium and Vitamin D can lead to low bone density. | Yes | Eat a diet rich in calcium (dairy, leafy greens) and vitamin D (fatty fish, fortified foods), or take supplements. |
| Exercise | Lack of weight-bearing and strength-training exercises can contribute to bone loss. | Yes | Engage in regular activities like walking, jogging, dancing, and lifting weights. |
| Hormone Levels | Low estrogen (in women) and low testosterone (in men) can accelerate bone loss. | Partially | Hormone replacement therapy may be an option; discuss with your doctor. |
| Lifestyle Choices | Excessive alcohol consumption and tobacco use weaken bones. | Yes | Limit alcohol intake and quit smoking. |
Can you improve your bone density?
While genetics and age play a significant role, you can take steps to improve or maintain your bone health. Lifestyle modifications and medical interventions are key.
- Nutrition: Ensure your diet includes sufficient calcium and vitamin D. Calcium is the primary building block of bones, and vitamin D is essential for your body to absorb that calcium effectively. Good sources include dairy products, fortified cereals and juices, and fatty fish.
- Exercise: Incorporate weight-bearing and strength-training exercises into your routine. These types of activities, which include walking, jogging, dancing, and weightlifting, stimulate bone growth and slow bone loss.
- Medication: For individuals with osteoporosis, a doctor may prescribe medication to slow bone loss or rebuild bone tissue. Regular DEXA scans help monitor the effectiveness of treatment.
- Prevent Falls: For older adults, falls are the primary cause of fractures due to low bone density. Taking measures like checking your home for hazards, improving your balance with exercises, and having regular vision checks can prevent serious injuries.
Conclusion
Determining if you have dense bones is not possible through physical symptoms alone. The only reliable way to measure bone mineral density is with a DEXA scan, a painless and non-invasive procedure. This test provides crucial information about your bone health and fracture risk, translating your results into a T-score to classify your bone density. While genetics and age are significant factors, a healthy diet, regular exercise, and certain medications can help maintain and improve bone density. Consulting a healthcare provider for screening recommendations is the best step toward understanding and protecting your bone health.
For more information on bone health and osteoporosis, you can visit the National Osteoporosis Foundation website. They offer comprehensive resources on risk factors, prevention strategies, and living with the condition. https://www.nof.org
