Understanding the Bone Density Test (DXA Scan)
Bone density testing, most commonly performed using a dual-energy X-ray absorptiometry (DXA or DEXA) scan, is a non-invasive medical procedure that measures your bone mineral density (BMD). The results help diagnose osteoporosis or osteopenia (low bone mass) before a fracture occurs, allowing for early intervention. The standard DXA scan measures bone density in the hip and spine, which are the most common sites for osteoporotic fractures.
Official Screening Recommendations for Women
Routine screening for women is more standardized than for men, primarily due to the hormonal changes that occur during menopause. The U.S. Preventive Services Task Force (USPSTF) and other health organizations provide clear guidance on this topic.
Women 65 and Older
For all women aged 65 and older, a routine bone density test is recommended. This is because the risk of osteoporosis and related fractures increases significantly with age, particularly after menopause, when estrogen levels decline and accelerate bone loss.
Postmenopausal Women Under 65
If you are a postmenopausal woman under 65, you may need earlier screening if you have specific risk factors for osteoporotic fracture. These factors are used in a clinical risk assessment tool to determine if your fracture risk is equivalent to or greater than that of a 65-year-old white woman with no additional risk factors. A healthcare provider can help you assess this risk.
Screening Recommendations for Men
Bone density loss is a concern for men as well, but screening guidelines are less uniform, as men lose bone mass more gradually than women.
Men 70 and Older
Some organizations, such as the Bone Health & Osteoporosis Foundation, recommend bone density tests for all men beginning at age 70. This recommendation acknowledges the increasing fracture risk that comes with advanced age in men.
Men 50 to 69 with Risk Factors
For men between 50 and 69, screening is typically considered on a case-by-case basis and is heavily influenced by risk factors. The USPSTF finds insufficient evidence for routine screening in men but advises clinicians to use their judgment, especially when risk factors are present. The Endocrine Society recommends testing for men in this age group who have significant risk factors.
Key Risk Factors that Prompt Earlier Screening
Regardless of gender, certain factors can increase your risk of developing osteoporosis and signal a need for earlier screening. These include:
- Low Body Weight: Being small and thin increases your risk of low bone density.
- Previous Fracture: A history of a fracture after age 50 from a low-impact fall can indicate weakened bones.
- Family History: A parental history of hip fracture or osteoporosis significantly increases your risk.
- Certain Medications: Long-term use of certain drugs, such as glucocorticoids (steroids), proton pump inhibitors (PPIs), or some medications for cancer or epilepsy, can cause bone loss.
- Medical Conditions: Conditions such as rheumatoid arthritis, kidney or liver disease, Type 1 diabetes, and hyperparathyroidism can increase risk.
- Lifestyle Choices: Excessive alcohol consumption, tobacco use, and a sedentary lifestyle are all detrimental to bone health.
What to Expect During a DXA Scan
- Preparation: You will be asked to wear loose, comfortable clothing without metal zippers, buttons, or buckles. Avoid taking calcium supplements for 24 hours before the test.
- Positioning: You will lie on a padded table. A technician may use a foam block to position your legs to help flatten your spine for the scan.
- The Scan: A scanner arm will pass over your body. The process is painless and typically takes 15 to 20 minutes. The machine uses a very low dose of X-ray radiation, comparable to what you would be exposed to naturally in a single day.
- Results: A healthcare provider will interpret your results, which include a T-score. This score compares your bone density to that of a healthy 30-year-old adult.
Comparison of Bone Density Tests
Several methods exist for assessing bone health, each with its advantages and limitations. DXA is the most widely recognized for diagnostic purposes.
| Feature | Dual-Energy X-ray Absorptiometry (DXA) | Quantitative Ultrasound (QUS) | Quantitative CT (QCT) |
|---|---|---|---|
| Technology | Low-dose X-rays | Sound waves | CT scans |
| Radiation | Very low radiation | No radiation | Higher radiation dose |
| Measurement Site | Central skeleton (hip, spine) | Peripheral sites (heel, finger) | Central skeleton (spine, hip) |
| Diagnosis | Gold standard for diagnosis | Used mainly for screening | Used mostly in research |
| Accuracy | High; measures BMD and microarchitecture (via TBS) | Less accurate than DXA | High; provides volumetric BMD |
| Portability | Requires hospital/clinic | Portable devices available | Requires hospital/clinic |
Strategies for Maintaining Strong Bones
If a bone density test reveals low bone mass, or if you simply want to prevent future loss, incorporating these healthy habits is key:
- Adequate Calcium and Vitamin D Intake: Calcium is a building block of bone, and vitamin D is essential for its absorption. Ensure you get enough through diet or supplements.
- Weight-Bearing Exercise: Activities like walking, jogging, dancing, and weightlifting put stress on your bones, which helps build and maintain density.
- Fall Prevention: Falls are a primary cause of osteoporotic fractures. Improving balance through exercises like Tai Chi and making your home safer (e.g., removing rugs) can reduce risk.
- Healthy Lifestyle: Quitting smoking and moderating alcohol intake are crucial steps for protecting bone health.
A Lifelong Commitment to Bone Health
Ultimately, the question of at what age do you do bone density testing is best answered in consultation with your healthcare provider. Your personal medical history, lifestyle, and risk factors will determine the most appropriate time for your first test. Early awareness and proactive measures can make a significant difference in preventing the debilitating effects of osteoporosis. For more information on maintaining bone health, visit the Bone Health & Osteoporosis Foundation for valuable resources and guides.
Conclusion
While age-based guidelines provide a starting point for bone density testing—primarily starting at 65 for women and 70 for men—a personalized assessment based on individual risk factors is always recommended. A DXA scan is a safe and effective tool for measuring bone strength and diagnosing conditions like osteoporosis early. By combining testing with healthy lifestyle choices, you can take control of your bone health and protect your mobility for years to come.
