What is low bone density?
Low bone density (sometimes called osteopenia) refers to bone density that is lower than the normal peak density but not low enough to be classified as osteoporosis. Bone density is a measurement of how dense and strong the bones are. If your bone density is low compared to normal peak density, you are said to have low bone density. Having low bone density means there is a greater risk that, as time passes, you may develop bone density that is very low compared to normal, known as osteoporosis.
What causes it?
Bones naturally become thinner as people grow older because, beginning in middle age, existing bone cells are reabsorbed by the body faster than new bone is made. As this occurs, the bones lose minerals, heaviness (mass), and structure, making them weaker and increasing their risk of breaking. All people begin losing bone mass after they reach peak bone density at about 30 years of age. The thicker your bones are at about age 30, the longer it takes to develop low bone density or osteoporosis.
Some people who have low bone density may not have bone loss. They may just naturally have a lower bone density. Low bone density may also be the result of one or more other conditions, disease processes, or treatments. Women are far more likely to develop low bone density and osteoporosis than men. This is because women have a lower peak bone density and because the loss of bone mass speeds up as hormonal changes take place at the time of menopause. In both men and women, the following things can contribute to low bone density:
- Eating disorders or metabolism problems that do not allow the body to take in and use enough vitamins and minerals
- Chemotherapy, or medicines such as steroids used to treat a number of conditions, including asthma
- Exposure to radiation
Having a family history of osteoporosis, being thin, being white or Asian, getting limited physical activity, smoking, and drinking excessive amounts of alcohol also increase the risk for low bone density and, eventually, osteoporosis.
What are the symptoms?
Low bone density has no symptoms. You notice no pain or change as the bone becomes thinner, although the risk of breaking a bone increases as the bone becomes less dense.
How is it diagnosed?
Low bone density is diagnosed with a bone density test, usually done to see whether you have osteoporosis. The most accurate test of bone density is dual-energy X-ray absorptiometry (DXA), although there are other methods. DXA is a form of X-ray that can detect as little as 2% of bone loss per year. A standard X-ray is not useful in diagnosing low bone density, because it is not sensitive enough to detect small amounts of bone loss or minor changes in bone density.
Osteoporosis Canada recommends that all women and men age 65 and older routinely have a bone density test to screen for osteoporosis. If you are at increased risk for fractures caused by osteoporosis, routine screening should begin sooner.footnote 1 Osteoporosis Canada recommends that you and your doctor check your fracture risk using a tool such as FRAX to help decide whether you should be screened for osteoporosis. Talk to your doctor about your risk factors and when to start bone density screening.
The FRAX tool can help predict your risk of having a fracture related to osteoporosis in the next 10 years. You can use this tool. Go to the website at www.sheffield.ac.uk/FRAX/tool.aspx?country=19 and fill out the questionnaire. If you have had a bone density test on your hip (femoral neck BMD), you can type in your score. If you have not had that test, you can leave the score blank.
How is low bone density treated?
Low bone density is treated by taking steps to keep it from progressing to osteoporosis and, for a few people, by taking medicine. Lifestyle changes can help reduce the bone loss that leads to low bone density and osteoporosis.
What you eat is very important to bone development. Calcium is the most critical mineral for bone mass. Your best sources of calcium are milk and other dairy products, green vegetables, and calcium-enriched products.
Your doctor may also want you to take a calcium supplement, often combined with vitamin D. Vitamin D helps your body absorb calcium and other minerals. It is found in eggs, salmon, sardines, swordfish, and some fish oils. It is added to milk and can be taken in calcium and vitamin supplements. In addition to what you take in from food, your body makes vitamin D in response to sunlight.
Exercise is important for having strong bones, because bone forms in response to stress. Weight-bearing exercises such as walking, hiking, and dancing are all good choices. Adding exercise with light weights or elastic bands can help the bones in the upper body. Talk to your doctor or a physiotherapist about starting an exercise program.
In addition to diet and exercise, quitting smoking and avoiding excessive use of alcohol will also reduce your risk of bone loss.
There are medicines for treating low bone density. But these are more commonly used if you have progressed past low bone density to the more serious condition of osteoporosis. Medicines that may be used for low bone density include bisphosphonates, raloxifene, and hormone replacement.
How can you prevent it?
Whether you will tend to develop low bone density is, in part, already determined. Things like whether you have any family members who have had osteoporosis or low bone density, whether you have a condition that requires you to take steroids, and how much calcium and vitamin D you got while you were growing up are beyond your control now. But if you are a young adult or if you are raising children, there are things you can do to help develop strong bones and prevent osteoporosis.
Your bones don't reach their greatest density until you are about 30 years old. So for children and people younger than 30, anything that helps increase bone density will have long-term benefits. To maximize bone density, make sure you get plenty of calcium and vitamin D through your diet and by spending a little time in the sun, get weight-bearing exercise on a regular basis, don't smoke, and avoid excessive alcohol. If you have children, teach them to eat healthy, get regular exercise, and avoid smoking and alcohol. Also, get them to play a little in the sunshine to help their bodies make more vitamin D. Talk with your doctor about how much and what sources of vitamin D are right for your child.
If you're older than 30, it's still not too late to make these lifestyle changes. A balanced diet and regular exercise will help slow the loss of bone density and delay or prevent osteoporosis.
What puts you at risk for low bone density?
Things that increase your risk include:
- Getting older.
- Having a family history of osteoporosis.
- Being thin.
- Being white or Asian.
- Getting too little physical activity.
- Drinking too much alcohol.
- Using certain medicines such as steroids.