Understanding the Bone Density T-Score
Bone density is typically measured with a Dual-Energy X-ray Absorptiometry (DEXA or DXA) scan, which is the most accurate method available. For postmenopausal women and men over 50, the results of a DEXA scan are reported as a T-score. This score is a comparison of your bone mineral density (BMD) to that of a healthy young adult at their peak bone mass, around age 30.
According to the World Health Organization (WHO), the diagnostic criteria for bone density levels are as follows:
- Normal Bone Density: A T-score of -1.0 or higher. A 70-year-old woman with a T-score in this range has bone strength comparable to a healthy young adult's peak bone mass.
- Osteopenia: A T-score between -1.0 and -2.5. This indicates low bone mass, meaning the bones are weaker than normal. This is a sign of increased risk for developing osteoporosis and potential fractures.
- Osteoporosis: A T-score of -2.5 or lower. This is a diagnosis of significant bone density loss, leading to a much higher risk of fractures.
It is essential to remember that while a normal T-score for a 70-year-old woman is technically -1.0 or higher, bone density naturally declines with age. Therefore, a score near the low end of the normal range for an older woman is common and does not necessarily indicate disease, but it does warrant careful monitoring. For context, one study noted that the average mean T-score for women between 65 and 75 years old was approximately -1.97.
Factors Affecting Bone Density in Older Women
Several factors contribute to the gradual decrease in bone density that is particularly pronounced in older women:
- Menopause and Estrogen Decline: The rapid drop in estrogen levels during and after menopause is one of the most significant risk factors for bone loss in women. Estrogen plays a crucial role in maintaining bone strength, and its decrease accelerates the process of bone resorption (breakdown).
- Age: The older a woman gets, the greater her risk of osteoporosis. Bone mass is lost faster than it is created as people age.
- Genetics and Family History: A family history of osteoporosis, particularly a parent or sibling with a history of fractures, can increase a woman's risk.
- Body Frame Size: Women with smaller body frames have less bone mass to begin with, which puts them at higher risk.
- Lifestyle Choices: A sedentary lifestyle, smoking, and excessive alcohol consumption all contribute to weaker bones.
- Dietary Factors: A lifelong diet low in calcium and vitamin D is a major contributor to reduced bone density.
- Medical Conditions and Medications: Certain conditions like rheumatoid arthritis, celiac disease, and thyroid hormone imbalances can affect bone health. Long-term use of corticosteroids also interferes with bone rebuilding.
Comparison of Bone Density Categories
| Bone Density Category | T-Score Range | Meaning for a 70-Year-Old Woman |
|---|---|---|
| Normal | -1.0 and above | Healthy bone density. Bones are strong and at a low risk of fracture. |
| Osteopenia | -1.0 to -2.5 | Low bone mass. Bones are weaker than normal, increasing the risk of future fractures. |
| Osteoporosis | -2.5 and below | Very low bone density. Bones are porous and brittle, leading to a high risk of fractures, especially in the hip, spine, and wrist. |
Strategies for Maintaining Bone Health After 70
Even after age 70, it is possible to maintain and even improve bone density and significantly reduce fracture risk.
Diet and Nutrition
Nutrition is a critical component of bone health at any age.
- Increase Calcium Intake: The recommendation for women over 50 is 1,200 milligrams of calcium per day, through a combination of diet and supplements if necessary. Excellent food sources include dairy products, leafy greens, fortified cereals, and canned fish with bones.
- Boost Vitamin D: Aim for 800 to 1,000 IU of vitamin D daily. It aids in calcium absorption and can be obtained from sunlight, fortified foods, and supplements.
- Ensure Adequate Protein: Protein is essential for bone formation and can help improve bone density, especially in older adults.
Regular Exercise
Consistent, bone-strengthening exercise is vital for slowing bone loss.
- Weight-Bearing Exercises: Activities that make you move against gravity are most effective. Examples include walking, dancing, hiking, and stair climbing.
- Strength-Training Exercises: Resistance training, using free weights, resistance bands, or weight machines, helps build muscle and bone strength.
- Balance Exercises: Activities like Tai Chi are excellent for improving balance and coordination, which reduces the risk of falls—a major cause of fractures in people with osteoporosis.
Fall Prevention
Since osteoporosis can make bones more fragile, preventing falls is extremely important. Practical steps include:
- Making the home safer by removing trip hazards like loose rugs.
- Using grab bars in bathrooms and stairwells.
- Ensuring good lighting throughout the home.
- Having regular vision and hearing check-ups.
Medical Management
For women with low bone density, medication may be necessary to prevent further bone loss and reduce fracture risk. The decision is based on a combination of factors, including T-score and other individual risk factors, which can be assessed using tools like the FRAX score. Your healthcare provider can discuss the various treatment options available, such as bisphosphonates, and determine the best course of action. For comprehensive information on bone health, you can visit the Bone Health & Osteoporosis Foundation website.
Conclusion
For a 70-year-old woman, a normal bone density is represented by a T-score of -1.0 or higher. However, scores between -1.0 and -2.5 (osteopenia) are common and indicate an increased risk that requires attention. Understanding your DEXA scan results is the first step toward managing your bone health. By adopting proactive strategies, including a calcium-rich diet, regular weight-bearing exercise, and discussing potential medications with a healthcare provider, you can effectively manage bone density and reduce the risk of fractures, promoting a more active and independent life in your senior years.
