http://www.hlth.gov.bc.ca/msp/protoguides/gps/bone/bonepg.html
Bone Density Measurement - Patient Information

Why is bone density testing so controversial?
Just about every aspect of bone research is a matter of hot debate. Several scientific reviews of the evidence have concluded that bone density measurement is poor at predicting which women will go on to have a fracture in later life. There are a number of reasons for this.

Bone density is only part of what makes a bone fragile. Bone strength cannot be measured directly since it depends on both bone density and microscopic bone structure, and there is no simple test to measure microscopic bone structure.

Low bone density is only one of many factors that can increase the risk of fracture. Factors such as inactivity, balance problems, poor vision, inappropriate footwear, the use of certain drugs, and household hazards can all increase the risk of falling and fracturing a bone. Some women believe that bone density testing and medical treatment of osteoporosis are examples of the "medicalization" of natural processes such as menopause and aging. "Medicalization" means treating natural processes like diseases and relying too heavily on highly technological medical treatments when less invasive approaches could be just as beneficial. On the other hand, some physicians believe bone density testing can provide valuable information and help women decide when hormone or drug treatment may be beneficial.

Bone density testing may not be perfect, but it's the only test available for osteoporosis. So, what have I got to lose?
You may be incorrectly diagnosed with osteoporosis and prescribed medication to treat a disease you don't have. If you start taking medication in your fifties, you may need to take it for 20 or 30 years to significantly reduce your risk of fracture. No medication is without risk. 

It includes the following sections:

Techniques

T and Z scores and the WHO definitions

Bone density distribution in young adults

Bone density losses with aging

Anatomic sites for measurement

Bone density and fracture risk

DEXA reports, step-by-step

BMAD

Standardizing results

Reproducibility

Ultrasound

Find the mistakes in BMD interpretation

Clinical indications for BMD

I found this article well worth reading and its accompanying graphs interesting. The section on the different rates of change due to aging in varying parts of the body was quite new to me. The article is so loaded with caveats that it almost seems to be saying that no reliance should be put on the numbers obtained! 

"In the last several years, many new techniques have been introduced for the measurement of bone density. At present, the clinician is faced with a choice between various technologies that provide measurements of different skeletal sites........In this article, the common clinical questions surrounding bone density measurements are reviewed, together with data supporting the appropriate skeletal site to measure to best  answer these clinical questions.

Confirmation of osteoporosis as defined by the World Health Organization (WHO)

Assessment of Fracture Risk
Several different studies have shown a strong relationship between bone density at virtually any skeletal site and the subsequent risk for fractures of the spine, hip, and forearm. The strength of this relationship depends on the type of fracture and the skeletal site measured.
(.....Almost all of the available data relating bone density to fracture risk has been obtained from elderly, primarily Caucasian, female populations. It remains to be shown that bone density measurements at age 50 will accurately predict fractures at age 70. However, the existing studies support this concept such that bone density has become a clinically accepted technique for assessing fracture risk...).

For determining *hip* fracture risk, data from the Study of Osteoporotic Fractures from more than 8000 women have show that  direct measurements of the hip are the most sensitive predictors of hip fracture . Heel measurements have also shown  excellent utility for predicting hip fracture, both with X-ray absorptiometry and quantitative ultrasound 

For the *spine*, data from the Hawaii Osteoporosis Study have shown a relatively comparable ability for spine, heel, forearm, and hand measurements to assess fracture risk. However, in this study where the mean age of the participants was 74 yr, it was possible that degenerative change may have influenced the spinal measurements, reducing the fracture relationship somewhat. It may be that direct spinal measurements in younger populations may be a more sensitive measure of vertebral fracture risk -- though this remains to be determined.

The use of bone density measurements to assess *overall* fracture risk has been addressed by the Rochester Epidemiological Project, a study of 304 women age 30-94 followed for a mean of more than 8 yr. This study, though performed with older photon absorptiometric techniques, showed a comparable ability for spine, hip, and forearm fractures for predicting overall fracture risk. However, the association between bone density and fracture was somewhat weaker than observed in shorter-term studies.

Monitoring skeletal change due to aging or in response to therapy. 
For assessing age-related bone loss, the metabolically active bone of the spine is often the most responsive skeletal site, particularly for women around the time of menopause. Studies performed by Harris et al. have confirmed that the largest decrements in bone density occur at the spine and heel within 2 yr of the menopause, whereas the hip and forearm show very little loss during this time 

With continued aging, the spine continues to be a sensitive monitor of bone loss, up until the age of 65 or so, when degenerative disease can mask any age-related changes [goes on to recommend imaging from the side as being more accurate]  Recently, results from the Early Postmenopausal Interventional Cohort (EPIC) have compared skeletal response for two common osteoporosis therapies, namely bisphosphonates and hormone replacement

For both the bisphosphonate and hormone-replacement [sounds like Prempro - Tishy] groups, the spine showed the greatest response after 2 yr of treatment. Both the PA and lateral spine showed equivalent response. The other skeletal sites also responded, but to a lesser degree than the spine. Thus, for the earliest detection of response to antiresorptive therapy, spinal measurements are preferred.

From the time of peak bone mass, bone loss occurs at all skeletal sites, though somewhat faster at the spine and less so at the hip and peripheral sites. At the time of menopause, spinal bone loss is accelerated because of the relatively high metabolic activity of the vertebral trabecular bone. Within a few years of menopause, bone loss at other skeletal sites also increases, but typically only after significant changes have already occurred in the vertebral body. Around age 70, relative bone mass at all skeletal sites begins to coincide, though bone loss at the spine often begins to be influenced by degenerative change, masking the age-related changes that continue at other skeletal sites.

- (up until roughly age 65), spinal measurements typically provide the most accurate measure of skeletal state and response to aging and/or therapy.
- (65 and older), the potential for a false negative at the peripheral skeleton is reduced, as the relative bone mass at the different skeletal sites begins to coincide more closely. Thus, for evaluating fracture risk, most skeletal sites can be expected to provide comparable information.

Osteopenia copyrighted 1994 by Michael L. Richardson, M. D

"One of the most common findings in skeletal radiology is increased radiolucency of bone, most properly termed osteopenia. This term is much preferred over terms such as "demineralization" or "undermineralization", since we really can't tell the exact mineral status of the patient's bone from the radiograph alone." 

This is a *long* article (complete with graphs, diagrams and xray illustrations) which includes all causes of osteopenia, though Richardson says that osteoporosis is the most common cause. 

He includes the gem 
Remember Resnick's Rule: "You can take a normal patient and an abnormal X-ray technician and produce osteoporosis at will."

"Accuracy defines how correct our measurement is compared to the true value. This is important for diagnosis 

Precision defines the variability occurring with repeated measurements over time. This is important for following changes over time of bone density of a patient. 

To be able to identify a change in bone density with a bone densitometer with a precision error of 1%, the actual change needs to be at least 2.8 % for it to be significant. Using equipment with an error of 5%, the actual change needs to be at least 14%. 

Normal bone loss just after menopause is appoximately 3% per year. " 

This site too has a page of osteoporosis links, some of them in Swedish... 
 

A national search to identify resources for people interested in increasing their dietary calcium led to lists of calcium-rich foods and some general recommendations. However, there were no useful guides to meal planning with kitchen tested recipes that were calcium-rich and healthy. 

           So the Hawaii Osteoporosis Foundation developed one! This month HOF will publish "Bone Appetit!", a delicious and unique collection of calcium-rich recipes. The authors, Dr. Joan Dobbs and Dr. Alan Titchenal have not just considered calcium in their recipes development; every recipe also meets the FDA's "healthy" guidelines for fat, sodium cholesterol and calories. "Bone Appetit!" also addresses different eating preferences including vegetarian diets such as lacto-ovo and vegan. "Bone Appetit!" also contains practical tips for increasing calcium in the diet, calcium guidelines and general preventive information on the foundations of good bone health 
 

Here is a sample of a delicious recipe for Orange Glazed Chicken with Peas and Potatoes for a taste of what this cookbook has to offer.  Visit the site for ordering information and a faxable order form.

 

STRONG WOMEN STAY YOUNG By Miriam E. Nelson, PhD   with Sarah Wernick   Bantam, 1997  The web site at http://www.strongwomen.com (extracts below)  has more info and links to research sites.

Most women begin to lose bone and muscle mass at about age 40; in part because of this, they start to slow down. And that's exactly what happened to the women who didn't exercise. One sedentary year later, their muscles and bones had aged, and they were even less active than before.

The women who lifted weights changed too - but in the opposite direction. After one year of strength training, their bodies were 15 to 20 years more youthful.

• They became stronger - often even stronger than when they were younger. 
• Without drugs, they regained bone, helping to prevent osteoporosis. 
• Their balance and flexibility improved. 
• They were leaner and trimmer, though eating as much as ever. 
• The women were so energized, they became 27 percent more active. 

A challenging, progressive strength-training program can build muscles and increase strength in women of all ages. But Miriam Nelson's study proved that the benefits go even further. Besides the great gains in strength, here's what strength training does: 

• Halts bone loss - and even restores bone 

• Improves balance 

• Helps prevent bone fractures from osteoporosis 

Hormones, calcium supplements and medications offer a degree of protection from bone loss. However, strength training not only builds bone, it cuts the risk of fractures by improving strength and balance to help prevent falls. What's more, all these benefits come without worrisome side effects.