The Better Bones Blog

by Dr. Susan Brown, PhD.

How accurate is a DEXA bone density test?

Nearly every day I see women and physicians themselves getting very worried when a woman’s bone density tests show even a small 1-2% decline. Women are often told their fracture risk has greatly increased and that they should immediately begin osteoporosis drug therapy. For many women, the growing “osteoporosis fear” is fueled by small reductions in bone density. But what do these small changes really mean, and just how accurate are the DEXA bone density tests anyway?

Thanks to the excellent work of the University of Washington osteoporosis specialist, Dr. Susan Ott, we now know that the common bone density test is rather imprecise and large changes in density are needed to assure that bone loss is indeed occurring, much less significant in nature. A thoughtful scientist, Dr. Ott had 300 patients get two bone density measurements: one when they came into the room, and the second after walking around the room for a while. With this simple experiment she showed that repeat measurements on the same day may show as much as 7% difference in bone mineral density. Breaking down the data she found that while a 4-6% change in bone mineral density indicates a “probably change” it takes more than a 6% change to fully guarantee a statistically significant change in bone density.

The Better Bones perspective on bone density testing: Bone density testing can be useful, especially when spaced over many years, but small changes are not significant and certainly not a basis for beginning bone drug therapy.

 

Reference:

Dr. Susan Ott’s website: http://courses.washington.edu/bonephys/opBMDp.html

 

How many people who fracture a hip are vitamin D deficient?

The recent explosion of research on vitamin D has made most of us aware that adequate vitamin D is essential for bone health. The degree of its importance, however, is underscored by world-wide research suggesting that practically everyone who experiences an osteoporotic (low-trauma) hip fracture has inadequate levels of vitamin D in his or her blood.

In Minnesota, they looked at 82 adult minimal trauma fractures in people ages 52-97. Ninety-seven percent of all 82 fractures were hip fractures. All but two of the hip fracture patients had low vitamin D levels (below 30 ng/mL). In a large British study, vitamin D deficiency was found in 95% of hip fracture patients as were 78% of hip fracture patients in a recent Boston study.

Such findings have led researchers to ask if vitamin D level is not the best predictor of hip fracture risk. Our research at the Center for Better Bones and the Better Bones Foundation would lead us to agree that low vitamin D should indeed be considered as a major, if not the major, risk factor for hip fracture.

 

References:

Gallacher, S.J. et al. 2005. Prevalence of vitamin D deficiency in Scottish adults with non-vertebral fragility fractures. CMRO, 21, 1355-1361.

Glowacki, J. et al. 2006. Importance of vitamin D in the design of hospital hip fracture care pathways. ASBMR Meeting Abstract #T46.

Malavolta, N. et al. 2005. The relationship of vitamin D status to bone mineral density in an Italian population of postmenopausal women. Osteoporos Int, 16, 1691-1697.

Simonelli, C. et al. 2005. Prevalence of vitamin D inadequacy in a minimal trauma fracture population. CMRO, 21, 1069-1074.

 

Tubal ligation linked to increased risk of spinal fracture

When I was researching the first edition of my book, Better Bones, Better Body, I came across a single scientific study reporting that tubal sterilization disrupted endocrine functioning and was likely linked to increased risk of fracture. As the body is one whole, interacting unit, it made sense to me that the natural hormonal flow would be disrupted by having the “tubes tied” and this might well impact bone health.

Research by Dr. Grace Wyshak from Harvard School of Public Health has confirmed this speculation. Tubal sterilization disturbs ovarian function and is associated with more menstrual and menopausal symptoms and an increased risk of vertebral fracture. Specifically, she found a 2.7 to 3.3 times increased risk of vertebral fracture among women who had undergone tubal sterilization.

This is important because tubal ligation is used more than any other single form of birth control in the US and worldwide. In 1995, 34.6% of ever-married US women between the ages of 35-44 had undergone tubal ligation. Little by little we are finding more hidden underlying causes of our current bone health crisis and discovering new areas of health maximization we need to work on. A safe, effective, yet bone-preserving birth control method is clearly one of them!

 

References:

Wyshak, G. 2005. Tubal ligation and the risk of vertebral fracture. Osteoporosis International, 16, 651-658.


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