DXA – or sometimes DEXA – scans are important for people in their 60s and above. They are also increasingly used by younger people interested in body composition.
A DXA – dual-energy X-ray absorptiometry – scan is an imaging test that uses low-dose X-rays to evaluate a person’s bone health, explains Dr Michael Perry, associate professor of radiology and medical imaging at the University of Virginia’s school of medicine. Most often, DXA scans are used to measure the strength and mineral content of an individual’s bones. This in turn helps determine that person’s risk of osteoporosis and bone fractures.
This is valuable information, as broken bones in older adults can be “the start of more serious health problems and can lead to long-term disability”, according to the National Institute on Aging.
DXA scans can also help estimate body composition including “fat percentage, muscle mass, and where fat is distributed throughout the body”, explains Dr Ann Malbas, an endocrinologist at the Mayo Clinic who specializes in bone diseases.
How exactly do DXA scans work and who needs one? We asked experts.
How do DXA scans work?
DXA scans are “safe, quick and painless”, says Malbas. During a scan, a person lies on a padded table while a scanning arm passes over their body. Two low-dose X-ray beams measure the amount of minerals in the bones, specifically in the hip and spine. It usually takes 10-20 minutes to complete.
The process is the same for measuring body composition, but instead of bone mineral density, it measures other elements, like total body fat percentage, fat distribution and lean mass.
Who should get a DXA scan?
“DXA is recommended for women aged 65 and older and men ages 70 years and older, as well as younger adults who have important risk factors,” says Dr Shadpour Demehri, professor of radiology and radiological science at Johns Hopkins University’s school of medicine.
Risk factors for low bone density, which may make a DXA scan advisable, include a previous broken bone from a minor fall or injury, long-term use of steroid medications like prednisone, a family history of osteoporosis or hip fractures, and certain medical conditions like COPD (chronic obstructive pulmonary disease).
Getting regular scans is important for high-risk populations, because osteoporosis is known as a “silent disease” – a condition most people don’t know they have until they experience a fracture. It’s also common, Malbas says, with osteoporotic fractures affecting one in three women and one in five men over age 50.
Because it is easy and uses relatively low levels of radiation, a DXA scan is considered safe for most populations, though Demehri says that “pregnancy is generally considered a reason to postpone the examination, because it involves ionizing radiation”.
People who have recently had imaging tests that include contrast material, like barium studies, may also have to delay their scans, as these materials can interfere with the accuracy of results, explains Malbas.
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As for those curious to know more about their body composition, DXA scans can provide a more accurate snapshot of one’s health.
“Often, people associate body weight with health, but body weight measurements only account for the total amount of someone’s tissue, and not what type of tissue,” says Perry. This matters because studies have shown that body composition may have a better correlation with health than overall weight.
“Someone may fall into the overweight category but may have large amounts of muscle but very little fat,” he says. “Conversely, a person with very low muscle mass may be at higher risk for falls and illness despite being ‘normal’ weight.”
Still, routine DXA scans are not essential for most young people, as they are “unlikely to provide information that changes medical care”, says Demehri. Regardless of whether one has high or low body fat, he explains, medical recommendations remain the same: “Regular physical activity, strength training, an optimally balanced diet and maintaining a proper weight remain the most important recommendations regardless of the exact body fat percentage,” he says.
What do you do if you have low bone density?
If a DXA scan reveals low bone density, several effective strategies can help reduce one’s risk of future fractures, says Demehri. These include:
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regular weight-bearing and resistance exercise
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adequate calcium and vitamin D intake
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avoiding smoking and excessive alcohol consumption
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prescription medications to strengthen bones
“Bone health and muscle health are closely connected,” Demehri adds. “Strong muscles help support the skeleton, improve balance and reduce the risk of falls, while healthy bones provide the structural framework for movement.”
