DXA scans, also known as dual-energy X-ray absorptiometry, are imaging tests that evaluate bone health and body composition. They are most commonly used to assess the risk of osteoporosis and bone fractures, particularly in older adults.
How DXA Scans Work
According to Dr Michael Perry, associate professor of radiology and medical imaging at the University of Virginia's school of medicine, DXA scans use low-dose X-rays to measure the strength and mineral content of bones. This helps determine a person's risk of osteoporosis and fractures, which can be particularly serious for older adults, as broken bones can lead to long-term disability.
Dr Ann Malbas, an endocrinologist at the Mayo Clinic, describes DXA scans as "safe, quick and painless." During the procedure, a person lies on a padded table while a scanning arm passes over the body, measuring bone minerals in the hip and spine. The scan typically takes 10-20 minutes. For body composition analysis, the same process measures fat percentage, muscle mass, and fat distribution.
Who Should Get a DXA Scan?
Dr Shadpour Demehri, professor of radiology at Johns Hopkins University, states that DXA is recommended for women aged 65 and older, men aged 70 and older, and younger adults with risk factors. These risk factors include a previous broken bone from a minor fall, long-term steroid use, a family history of osteoporosis or hip fractures, and conditions like COPD.
Osteoporosis is often called a "silent disease" because it shows no symptoms until a fracture occurs. It is common, affecting one in three women and one in five men over age 50, according to Malbas. Regular scans are important for high-risk groups to catch the disease early.
Safety and Considerations
DXA scans are considered safe for most people due to low radiation levels. However, Demehri notes that "pregnancy is generally considered a reason to postpone the examination, because it involves ionizing radiation." People who have recently had imaging with contrast materials, like barium studies, may also need to delay their scans, as these can affect accuracy.
Body Composition Insights
For those interested in body composition, DXA scans offer a more accurate picture than weight alone. Perry explains that body weight doesn't distinguish between muscle and fat, and studies show body composition correlates better with health. Someone may be overweight but have high muscle mass, while another with normal weight may have low muscle mass and higher risk of falls and illness.
However, routine DXA scans are not essential for most young people, as they are "unlikely to provide information that changes medical care," says Demehri. He emphasizes that regardless of body fat percentage, medical recommendations remain the same: regular physical activity, strength training, a balanced diet, and maintaining a proper weight.
If You Have Low Bone Density
If a DXA scan reveals low bone density, strategies to reduce fracture risk include regular weight-bearing and resistance exercise, adequate calcium and vitamin D intake, avoiding smoking and excessive alcohol, and prescription medications to strengthen bones. Demehri adds, "Bone health and muscle health are closely connected. Strong muscles help support the skeleton, improve balance and reduce the risk of falls, while healthy bones provide the structural framework for movement."
