What is a DXA scan?


Are you going through menopause or approaching that stage of life? If so, you may have heard about the importance of bone health during this time. As women age, they are at an increased risk for developing osteoporosis, a condition in which bones become weak and brittle and are more likely to fracture. But did you know that there's a simple test that can help assess your bone health and determine your risk for osteoporosis? It's called a DXA scan.

A DXA (dual-energy X-ray absorptiometry) scan is a quick and painless test that measures bone mineral density (BMD) in different parts of the body, such as the hip, spine, and wrist. You lie on a table while the scanner arm passes over your body, generating images that are analyzed by a computer to calculate your bone mineral density.  The test uses a very small amount of ionizing radiation to produce two X-ray beams of different energy levels, which are absorbed differently by bone and soft tissue. The difference in absorption between the two beams allows for the calculation of bone mineral density. However, it can also provide information about body composition, including the amount of fat and lean tissue. 

What do the results mean?

The results of the DXA scan are reported as a T-score, which compares your bone mineral density to that of a healthy young adult of the same sex and ethnicity.

The T-score can help determine your risk for osteoporosis. A T-score of -1.0 or higher is considered normal, while a T-score between -1.0 and -2.5 indicates low bone mass (osteopenia), and a T-score of -2.5 or lower indicates osteoporosis. If you receive a diagnosis of osteopenia or osteoporosis, your healthcare provider may recommend lifestyle changes such as exercise and diet modifications, as well as medications to improve bone health.


Why is a DXA scan important during menopause?

During menopause, women experience a decrease in estrogen production, which can lead to a loss of bone density. This loss of bone density can put women at an increased risk of developing osteoporosis. A DXA scan can help identify women who are at risk for osteoporosis and may benefit from lifestyle changes or medication to prevent bone loss. 

In addition, a DXA scan can be used to monitor bone density over time, allowing doctors to detect changes and intervene early if necessary. This is important because bone loss can occur gradually over many years, often without symptoms until a fracture occurs. By monitoring bone density, doctors can identify women who are at risk for fractures and take steps to prevent them. 

How often should you get a DXA scan?

The answer depends on a few factors, including your age, risk factors for osteoporosis, and the results of previous DXA scans. In general, the National Osteoporosis Foundation recommends that women get a baseline DXA scan at age 65, or earlier if they have risk factors for osteoporosis. If the results of the baseline scan are normal, women can wait up to 10 years for their next DXA scan. However, if the results show low bone mass or osteoporosis, women may need to get scans more frequently.

For postmenopausal women under age 65, the decision to get a DXA scan should be based on individual risk factors for osteoporosis. For example, if you have a family history of osteoporosis, are underweight, or have a history of fractures, your healthcare provider may recommend getting a DXA scan earlier than age 65. If you have been diagnosed with osteopenia or osteoporosis, your healthcare provider may recommend getting DXA scans more frequently to monitor changes in bone density and the effectiveness of treatment.

How do I use DEXA scan results?

  • Do I need medication?

Whether or not you need to take medication for low bone mineral density depends on a number of factors, including the severity of your condition, your risk of fractures, and your overall health status.

If you have low BMD but are not at high risk of fractures, your doctor may recommend lifestyle changes and non-medication interventions to help improve your bone health. These might include weight-bearing exercise, a healthy diet rich in calcium and vitamin D, and avoiding smoking and excessive alcohol consumption.

However, if you have low BMD and are at high risk of fractures or have already experienced a fracture, your doctor may recommend medication to help improve your bone health and reduce your risk of future fractures. The type of medication recommended will depend on a number of factors, including the underlying cause of your low BMD and any other medical conditions you may have.

Common medications used to treat low BMD include bisphosphonates, which work by slowing down bone breakdown, and denosumab, which works by blocking a protein that breaks down bone. Other medications that may be recommended for certain individuals include hormone replacement therapy, teriparatide (a medication that stimulates bone formation), and calcitonin (a medication that slows down bone loss).

Ultimately, the decision to take medication for low BMD should be made in consultation with your doctor, who can help you weigh the benefits and risks of different treatment options based on your individual circumstances.

 

  • Do I need to see a registered nutritionist/dietician?

It can be beneficial to see a registered nutritionist if you have low bone mineral density (BMD), as diet plays an important role in bone health. They can help you develop a healthy eating plan that is rich in the nutrients needed for strong bones, such as calcium, vitamin D, magnesium, and vitamin K.

Calcium is a key nutrient for bone health, and getting enough calcium in your diet is essential for maintaining strong bones. However, it's important to ensure that you are also getting enough vitamin D, as this vitamin is necessary for the absorption of calcium from the diet.

A registered nutritionist can work with you to identify food sources of these and other important nutrients and can help you develop a meal plan that meets your individual needs.

 

  • Do I need to do strength training?

Strength training has been shown to have a positive impact on bone mineral density as the mechanical stress of resistance training stimulates bone cells to produce new bone tissue. Over time, this can lead to an increase in bone mineral density, particularly in the weight-bearing bones such as the hips and spine.

Research has shown that strength training can be an effective way to prevent and treat osteoporosis. In fact, the National Osteoporosis Foundation recommends strength training as one of the key components of an osteoporosis prevention and management program.

It's important to note that the extent of the impact of strength training on BMD can vary depending on a number of factors, including the intensity and frequency of the training, the individual's age and gender, and their baseline BMD. Nonetheless, strength training is generally considered to be a safe and effective way to improve bone health and reduce the risk of osteoporotic fractures.

Where can I get a DXA scan in Hong Kong?

One place that offers DXA scans is the Active Health Clinic at The University of Hong Kong. The clinic provides comprehensive health assessments and personalised lifestyle advice to help individuals achieve and maintain optimal bone health. The scan and an explanation of your results take around 30 minutes!

(1) Greendale G.A., Sowers M.F., Han W. Bone mineral density loss in relation to the final menstrual period in a multiethnic cohort: results from the Study of Women's Health Across the Nation (SWAN) J Bone Miner Res. 2012;27:111–118. 

(2) Garnero P., Sornay-Rendu E., Duboeuf F., Delmas P.D. Markers of bone turnover predict postmenopausal forearm bone loss over 4 years: the OFELY study. J Bone Miner Res. 1999;14:1614–1621.

(3) Massini DA, Nedog FH, de Oliveira TP, Almeida TAF, Santana CAA, Neiva CM, Macedo AG, Castro EA, Espada MC, Santos FJ, Pessôa Filho DM. The Effect of Resistance Training on Bone Mineral Density in Older Adults: A Systematic Review and Meta-Analysis. Healthcare (Basel). 2022 Jun 17;10(6)



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