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Answers to popular questions about DEXA Bone Density Scans
What is a Dexa Scan Used For?
Bone density scans (DEXA) are often used to diagnose or assess your risk of bone weakening conditions, one example being osteoporosis, a health condition that reduces the strength of bones and makes them more likely to break. The more dense your bones, the stronger and less likely they are to break (fracture). Osteoporosis does not cause any symptoms until a bone is broken and can affect anyone at any age.
You may need to have a bone density scan if you’re:
• over 50 with a risk of developing osteoporosis
• under 50 with other risk factors, such as smoking or a previous broken bone
A bone density scan compares your bone density with the bone density expected for a young healthy adult or a healthy adult of your own age, gender and ethnicity.
The difference is calculated as a standard deviation (SD) score. This measures the difference between your bone density and the expected value.
The difference between your measurement and that of a young healthy adult is known as a T score,
The difference between your measurement and that of someone of the same age is known as a Z score.
The World Health Organization classifies T scores as follows:
• above -1 SD is normal
• between -1 and -2.5 SD is defined as mildly reduced bone mineral density (BMD) compared with peak bone mass (PBM)
• at or below -2.5 SD is defined as osteoporosis
If your Z score is below -2, your bone density is lower than it should be for someone of your age. Z scores are usually used for children and people under 30 who are still growing.
Although BMD results provide a good indication of bone strength, the results of a bone density scan will not necessarily predict whether you’ll get a fracture.
For example, someone with low bone density may never break a bone, whereas someone with average bone density may have several fractures.
This is because other factors, such as age, sex or whether you have previously had a fall, also determine if you’re likely to sustain a fracture.
Your doctor will consider all of your individual risk factors before deciding if treatment is necessary.
Osteoporosis is a health condition which increases as we age and causes bones to become weak and fragile and prone to breaking, even after a low-impact injury. It can affect anyone, at any age.
According to the Royal Osteoporosis Society (www.theros.org.uk) one in two women and one in five men in the UK over the age of 50 will break a bone due to osteoporosis, so the condition is very common. Reduced levels of oestrogen accelerate the breakdown of bone tissue, so the condition is more common in post-menopausal women
The skeleton is continually breaking down old bone and growing new bone. If the body can’t make new bone fast enough or it breaks down old bone too fast, bone mass decreases and osteoporosis develops.
Osteoporosis affects over 2 million people in the UK. Every year, 300,000 people suffer a fragility fracture (a broken bone resulting from a fall a standing height or less), including over 70,000 hip fractures.
Fractures cause significant pain, disability and loss of independence for patients and in many cases can be fatal. Indeed, 1500 people die every month in the UK following a hip fracture.
Osteoporosis has no obvious symptoms and very often, people don’t know they have osteoporosis until they suffer a fracture and so many call it the “Silent Disease”.
Just treating hip fractures as a result of osteoporosis has an enormous impact on NHS budgets – current estimates suggest the cost at £5million per day, a figure which is set to continually rise as the population ages.
In women, the process of breaking down more bone than we are making is more pronounced during the years of the menopause. Lower levels of oestrogen, calcium and vitamin D are all important factors as well as hormone levels of progesterone and testosterone. The loss of oestrogen in and following the menopause can result in less bone renewal, resulting in thinner or less dense bones that are more prone to fracture.
Osteoporosis becomes more common as we go through the menopause and at the age of 50, around 2% of women have osteoporosis. This increases to 25% by the age of 70
A woman can lose up to 20% of her bone density during the 5-7 years following the menopause
(* source: Osteoporosis UK
Men and osteoporosis
Approximately 25% of hip fractures related to osteoporosis occur in men.
As men age, loss of testosterone is a key reason for osteoporosis development. Excessive alcohol consumption and smoking area also factors along with insufficient exercise. Exercise may only need to consist of regular strenuous walking to aid bone and muscle strengthening.
People with the following conditions may also be at significantly increased risk of developing osteoporosis:
Type 1 diabetes
IBD – Inflammatory bowel disease
Chronic kidney disease
Oestrogen and testosterone deficiency
COPD – some lung diseases
Eating disorders – anorexia
Overactive thyroid and diseased of parathyroid gland
In addition, patients who are on certain drug regimes may need regular bone density scans to check the medication effect on their bone density (such as steroids)
Other risk factors for developing osteoporosis are:
History of broken bones
How does a DEXA scan work
Some radiation is absorbed by the bone and soft tissue, and some travels through your body.
Special detectors in the DEXA scanner measure how much radiation passes through your bones, and this information is sent to a computer. The computer compares your results with the bone density of a healthy adult of your own age, gender and ethnicity.
A DEXA scan is more effective than a ‘standard’ X-ray at diagnosing low bone density. However as a DEXA scan does still use low levels of radiation, it is not recommended to have a scan more than once a year and our team will advise you on this.
Patients can have the DEXA scan in a large room and are not enclosed in a small place
The DEXA scan generally takes between 15-25 minutes and patients are asked to change into a gown for their scan. Our team will also ask you to remove any metal objects on your clothes like zips, belts, clasps, bras and piercings before your scan.
We will give you your results on the day of your scan appointment.
Is a DEXA scan /Body Composition scan safe?
Bone density scans are very safe. They use a much lower level of radiation than standard X-rays, which means that the technical specialist carrying out the scan can stay in the scanning room with you during the scan.
The risk of this radiation causing any problems in the future is incredibly small. The DexaStrong team will make sure the benefits of having the scan outweigh any risk there may be from radiation.
Despite being very safe, bone density scans and X-rays are not recommended for pregnant women, as X-rays can damage an unborn child. We would also not recommend having a DEXA scan more than once a year and you can discuss this with our DexaStrong Clinic team.