To track the health of its population, the federal government undertakes a massive health survey of the U.S. population every two years, known as the National Health and Nutrition Examination Survey (NHANES). Beginning in 2005, the survey has included bone mineral density measurements — and the most recent report shows a generalized decline in bone density. What’s the reason for this?
Bone density’s sudden downward spiral
These national surveys study a multi-ethnic sample of non-institutionalized individuals age 30 and over. Between 2005 and 2010, NHANES data showed bone mineral density to be fairly stable, which seemed to correlate with the slight decrease in hip fracture incidence reported by other researchers. But when they measured bone mineral density in 2014, they found a significant and generalized decrease in bone density.
Survey cycles Bone Mineral Density
2005-2006 Generalized stability of bone density
2007-2008 Generalized stability of bone density
2009-2010 Generalized stability of bone density
2010-2014 Generalized significant decline in bone density
What’s the reason for this?
Take a look at what else happened to us as a population between 2005 and 2014
- The percentage of people with a sedentary lifestyle more than tripled — in women, 9.59% reported being physically inactive in 2005 compared to 31.82% in 2014, while in men, 87% reported being physically inactive in 2014 compared to 22.83% in 2005.
- Not surprisingly, the percentage of people with hypertension also increased, from 35.4% to 45.08% from 2005 to 2014.
- Equally predictably, the percentage of self-reported diabetes increased 6% for both men and women
To me, it looks as though our ever-increasing lack of physical activity is catching up with our bones and our body, resulting in declining bone density. It makes sense. Exercise, even in small amounts, is known to positively affect inflammation, stress, cardiovascular health, and, of course, our bones. It stands to reasons that all of these would suffer if we spent too much time sitting.
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Xu Y, Wu Q. Decreasing trend of bone mineral density in the US multiethnic population: analysis of continuous NHANES 2005-2014. Osteoporosis Int(2018) 29:2437-2446.
I’m Dr. Susan Brown. I am a nutritionist, medical anthropologist, writer, and speaker. Get my free weekly newsletter here.