It’s easy to take your bones for granted—until you break one. As we grow older, our bones become weaker and more brittle because of reduced density, loss of mass, and deterioration of bone architecture. Bone strength peaks in early adulthood and then gradually declines. For women this process accelerates during the years around menopause, but older men develop brittle bones, too. Genetic, dietary, and lifestyle factors, along with general health, also play key roles in bone health.
Most people don’t realize that bone is active, living tissue that continually rebuilds itself. This remodeling process is a kind of preventive maintenance program, constantly removing old bone and replacing it with new bone. Bones are made of collagen, a fibrous protein that’s woven into a flexible framework, and hydroxyapatite, a bone mineral that is mostly calcium and that hardens the framework. Bone loss occurs when there’s greater removal than replacement, an imbalance that becomes more likely with advancing age.
Be good to your bones
Building bone and maintaining it is a lifetime proposition. Ideally, the time to start thinking about bone health is before adulthood—though few young people do. In order to maximize bone density, adolescents and young adults need a healthy calcium-rich diet plus weight-bearing exercise. That way, when bone density starts to decline, usually in one’s thirties, they’ll have lots of bone to draw on—like money in the bank.
Nearly everyone who lives long enough will experience significant bone loss. Age-related bone loss averages 0.5 to 1 percent per year, and the rate doubles for women during and around menopause (beginning a few years before the last menstrual period and continuing a few years after cessation of menses), largely because of hormonal changes.
When the weakening is severe, bones become fragile and brittle—a condition called osteoporosis (from the Latin, meaning porous bones), which increases the risk of fractures. About one-half of all white women and one-fifth of white men will have an osteoporosis-related fracture in their lifetime. (African Americans have lower rates of osteoporosis.) More than three-quarters of these fractures occur after age 75. Such fractures often occur following minimal or even no trauma or impact. Particularly in older people, a hip fracture (which involves the upper portion of the thigh bone, or femur) can have devastating effects, often leading to permanent loss of mobility and independent living and increasing mortality rates.
When bone loss is less severe, it is called osteopenia or simply low bone density—a “pre-disease” (along the lines of prediabetes and prehypertension) that may progress to osteoporosis. In a sense, osteopenia was first demarcated and classified as a disorder in the mid-1990s, when a panel of experts associated with the World Health Organization and sponsored in part by the drug industry defined it based on results from bone mineral density (BMD) tests.
Osteopenia: all too common
Debate continues about whether diagnosing osteopenia leads to the medical classification of a predictable aspect of aging and to potential overtreatment. After all, about one-third of American women ages 50 to 65 and two-thirds of those over 65 who are tested will be told they have low BMD, usually osteopenia (though after age 75, about half have full-blown osteoporosis). That’s about 43 million Americans with osteopenia, plus 10 million with osteoporosis, including 2 million men.
There is a continuum of risk: As BMD decreases, fracture risk gradually increases. Though people with osteopenia are at lower risk for fractures than people with osteoporosis, they are at elevated risk compared to those with normal BMD. Still, many of them never go on to develop osteoporosis or have fractures. Thus, the conundrum about treating osteopenia.
Of course, it makes sense for anybody with osteopenia—and even those without it, at young ages—to take steps to keep their bones strong, such as consuming enough calcium and vitamin D and doing weight-bearing exercise (see 7 Ways to Reduce Osteoporosis Risk below). A diagnosis of osteopenia should provide extra motivation to do all that.
What about drugs for osteopenia?
Many drugs originally approved by the FDA as treatment for osteoporosis, notably bisphosphonates, were subsequently approved for its prevention—that is, to treat osteopenia (see Prescription Drugs for Osteoporosis and Osteopenia). Should tens of millions of women, and many older men as well, take these drugs if all they have is osteopenia? Isn’t early treatment always a good idea? Many doctors say yes, as do countless ads for the drugs, which often target younger women and strongly suggest that the sooner you start, the better.
On the other hand, critics charge that osteopenia is a creation of the pharmaceutical companies and manufacturers of bone-density testing machines, which profit from increased treatment. Certainly, the drug industry funds a great many of the studies relating to bone health, as well as medical conferences and advocacy groups.
Bone Loss: Tallying Your Risk
The more of these risk factors you have, the more likely you are to have or develop osteoporosis.
What a BMD test tells you
Osteoporosis used to be diagnosed, for the most part, only after a low-impact fracture. In the late 1980s, the advent of a special type of X-ray called DXA (dual-energy X-ray absorptiometry) to measure BMD allowed for earlier diagnosis.
The influential U.S. Preventive Services Task Force recommends that women start DXA screening for BMD at age 65. It also advises DXA for younger women whose risk factors for fracture put them on par with a 65-year-old woman who has no additional risk factors. Other expert groups recommend that all postmenopausal women, along with men over 50, be evaluated for osteoporosis and fracture risk (often using a tool such as FRAX) and that those found to be at high risk should begin DXA screening and make appropriate lifestyle changes.
Because of insufficient evidence, the Task Force has no screening recommendation for men who have had no previous fracture. But the Endocrine Society, National Osteoporosis Foundation, and some other expert groups recommend that men be screened with DXA at age 70, earlier if they are at elevated risk for fractures. About one-third of all osteoporotic hip fractures worldwide occur in men, who are more likely than women to die the year after such a fracture. Male smokers and those with chronic obstructive pulmonary disease (COPD) are at especially high risk. Yet men are far less likely to be assessed for bone loss and treated.
BMD testing may also be done if you have back pain that could be caused by a vertebral fracture or if you have lost significant height. When regular DXA testing is not available, devices that measure bone in the lower arm, wrist, finger, or heel may be used, but the results are less accurate, and you’ll still need a regular DXA test to confirm the results. By the way, DXA emits far less radiation than most medical scans— your exposure is less than what you’d get on a transcontinental flight.
Results of BMD testing, usually done at the hip (notably the narrow “neck” of the femur, just below the hip joint) and spine, are expressed as a T-score. This is the number of units (called standard deviations) that a person is above or below the BMD of an average woman in her twenties. A negative number means you have thinner bones; the larger the negative number, the greater the bone loss. That is, a T-score of -1.0 is lower (worse) than a T-score of -0.5, and -3.5 is lower (worse) than -3.0.
|Normal bone density||-1 and above|
|Osteopenia||-1 to -2.5|
|Osteoporosis||-2.5 and below|
Because T-scores compare BMD to that of a young woman, most postmenopausal women and nearly all women over 75 fall into the osteopenia or osteoporosis ranges.
You may also get a Z-score. In contrast to a T-score, this compares your BMD with what’s normally expected for the average person your age, sex, and race/ethnicity. A Z-score of -2 is considered significantly below the expected range for that age and thus indicates elevated risk. Of course, since average BMDs are low at older ages, by using them as comparisons, Z-scores designate fewer people as being at high risk.
You will, of course, need professional advice to interpret all this.
Two things to keep in mind: All of these cutoffs are somewhat arbitrary, even according to the panel of experts who chose them. The difference, say, between T-scores of -2.4 and -2.6—crossing the line between osteopenia and osteoporosis—may not be clinically meaningful, and could even simply result from using different DXA machines.
In addition, bone density (that is, quantity of bone) isn’t everything when it comes to evaluating bone health. Bone quality and structure—including the micro-architecture of bone, size of the mineral crystals, and quality of collagen (connective tissue)—are also important. DXA cannot evaluate these factors, and there are no routine screening tests for them. But researchers look at such factors when studying treatments for osteoporosis and bone health in general, and such ways of screening may become routine in the future.
If DXA testing determines that you have osteopenia, that by itself doesn’t mean you should start taking bone-building drugs. The next step is to evaluate your risk factors with your doctor.
In 2008, a study group associated with the World Health Organization developed a computer-based, country-specific fracture risk assessment tool called FRAX to determine the 10-year probability of a hip or other major fracture. By filling in your age, sex, height, weight, fracture history, smoking status, and other factors, including BMD (preferably the T-score of your femoral neck), you can calculate your risk of fracture over the next 10 years. (If you don’t have a T-score, FRAX can still give you a rough estimate.) It’s best to do this with your health care provider, who can help you evaluate the results, but you can also fill it in yourself.
The Foundation for Osteoporosis Research and Education provides a similar online risk calculator.
FRAX can help people with T-scores in the osteopenia range decide whether they should consider taking medication to reduce fracture risk. The guidelines that accompany the results suggest that treatment be considered if the 10-year risk of a hip fracture is calculated to be 3 percent or higher, or the 10-year risk of a major osteoporotic fracture (hip, vertebrae/spine, humerus, or wrist) is 20 percent or higher. If fracture probability is less than those cutoffs, “clinician’s judgment and/or patient’s preferences” may still lead to consideration of medication, each FRAX report states. If you’ve never had your BMD measured and FRAX suggests that you are at high risk for fracture, you should have a DXA test.
Though FRAX has become standard in clinical practice, many of the advocacy and medical organizations that supported the development of this tool and the T-score cutoffs were heavily funded by the pharmaceutical industry, according to an analysis in BMJ in 2015. Some critics thus see FRAX as essentially a tool to get more people to take osteoporosis drugs.
People who have BMD in the osteoporosis range or have had a fracture that’s likely related to the disease should strongly consider taking medication. Only about one-fifth of such people do so. First, however, it is essential to have a careful medical evaluation, since low BMD may result from conditions such as hyperparathyroidism, osteomalacia, or chronic kidney disease, in which case osteoporosis drugs may be inappropriate. In some cases, treating an underlying disease, such as celiac disease or Cushing’s syndrome, can help halt or slow further bone loss. Before prescribing bisphosphonates, doctors should check for low blood levels of vitamin D (and, if necessary, advise supplements), as well as assess kidney function.
What about people with osteopenia who have not had a fracture? There are too many unanswered questions to recommend osteoporosis medication in most cases, especially since the evidence about the drugs’ benefits for such people is limited and inconsistent. This is especially true when FRAX does not show a high 10-year fracture risk and when osteopenia is mild (-1.0 to -1.5). Moreover, if your T-score indicates you have osteopenia but it is fairly stable over time—particularly if the bone loss is mild—there is usually no reason to take medication.
In some cases, medication to treat osteopenia does make sense—notably when the calculated 10-year fracture risk is very high (because of family history, for instance). And osteoporosis medication may benefit people with osteopenia who have to take drugs that can worsen bone loss, such as glucocorticoids, aromatase inhibitors, and androgen deprivation therapy.
How often should you have your BMD measured? While there are no official recommendations for optimal screening intervals, Medicare guidelines suggest that retesting every two years is standard for most people with osteoporosis. There’s some evidence that if you have moderate to advanced osteopenia, testing every 2 to 5 years is appropriate. For women with mild osteopenia, it takes about 15 years for 10 percent of them to progress to osteoporosis, according to a study in the New England Journal of Medicine in 2012.
There are no official treatment targets for medication other than to halt bone loss or possibly increase BMD. Any increases are generally small, but even small changes can be meaningful when it comes to BMD.
7 Ways to Reduce Osteoporosis Risk
These lifestyle steps will help you cut your risk of excessive bone loss and osteoporosis.
Bottom line: Decisions about treatment for osteoporosis or osteopenia should be individualized, based on shared decision-making between patients and health care providers, including a discussion of the rare but potentially serious adverse effects of the drugs. Decision aids such as the one from the Mayo Clinic can be helpful.
The importance of lifestyle factors such as weight-bearing exercise, not smoking, eating well, and reducing the risk of falls should not be underestimated, even in people taking bone-building drugs. It’s especially important for people diagnosed with low BMD to stay active. They often become fearful of falling and thus limit their physical activities, which is bad for their bones.
Published August 15, 2017