so called “bone density tests” do not truly measure bone mineral density. This is because bone density machines are highly influenced by area or size. For example, small-boned or thin people are likely read as having lower bone density than they really have.
I was excited to see two different research projects looking at bone density cross-culturally to confirm this theory.
- The first study looked at bone density of premenopausal and perimenopausal women in the US from four different ethnic groups — Caucasian, African-American, Japanese and Chinese. Although simple bone density measurements found striking differences in bone density between women of different ethnic backgrounds, among women of comparable weight there were no differences found in lumbar spine BMD (bone mineral density) in African-American, Chinese, and Japanese. BMD of the hip bone in women of similar weight was also similar in Chinese, Japanese, and Caucasians. When compared by bone size, Chinese women were found to have a lumbar BMD equal or above those of Caucasians and Japanese women.
- The second study compared the bone mineral density of Chinese, Indian, European, and Polynesian women living in New Zealand. The commonly measured BMD of these ethnic groups showed Chinese and Indian women having significantly lower BMD than Caucasians, but the European women were taller. When the numbers were adjusted for height, the differences in bone density between Caucasians, Indians and Chinese were almost completely eliminated. Polynesian women presented a different case. They were significantly more obese and had a higher bone mineral density even after adjustment for body size.
The take home message is that bone and body size, height and weight make a difference in bone density testing, and current bone density testing underestimates the bone density of thin or small individuals. One day we will see bone density tests better adjusted for these variables. In the meantime, if you are thin, small boned, or short, expect that your bone density measurement may likely show lower densities than larger and heavier women of your age group.
Learn for yourself what you test results mean with my new DVD, “How To Read Your Bone Density Test.”
Finkelstein, J., et al. 2002. Ethnic variations in bone density in premenopausal and early perimenopausal women: effects of anthropometric and lifestyle factors. J of Clin Endo & Metabol, 87(7), 3057-3067. URL:http://jcem.endojournals.org/cgi/content/abstract/87/7/3057 (accessed 10.27.2010).
Cundy, T, et al. 1995. Sources of interracial variation in bone mineral density. J of Bone Min Research, 10(3), 368-373. URL:http://onlinelibrary.wiley.com/doi/10.1002/jbmr.5650100306/pdf (accessed 10.27.2010).