Lumbar spine and proximal femur bone mineral density, bone mineral content, and bone area: United States, 2005-2008

OBJECTIVE: This report presents bone measurement data from dual-energy X-ray absorptiometry scans of the lumbar spine and proximal femur for persons aged 8 years and over from the National Health and Nutrition Examination Survey (NHANES) 2005-2008.

METHODS: Means, standard deviations, and selected percentiles were calculated for the proximal femur and lumbar spine (total and subregions) by sex, race and ethnicity, and age. Smoothed mean total lumbar spine and femur neck bone mineral density (BMD) were plotted by age, sex, and race and ethnicity. Multiple regression was used to test for significant interactions and to calculate mean total lumbar spine and femur neck BMD after adjusting for age, sex, and race and ethnicity. Differences by sex, race and ethnicity, and age were summarized by calculating the percent difference in adjusted means.

RESULTS: Among scanned individuals, 11% lacked total lumbar spine data due to invalid data for one or more lumbar vertebrae, and 4% had invalid data for the proximal femur. Non-Hispanic black persons had 6% higher total lumbar spine BMD and 9%-10% higher femur neck BMD than non-Hispanic white persons. Mean total lumbar spine BMD and femur neck BMD did not differ between Mexican-American and non-Hispanic white persons in those under age 20. For those aged 20 and over, Mexican-American persons had 4% lower total lumbar spine BMD but 1% higher femur neck BMD than non-Hispanic white persons. Mean total lumbar spine BMD was 8%-17% higher in females aged 8-15 compared with males of the same age. In the age group 16-49, mean total lumbar spine BMD was similar or slightly higher for females compared with males, but after age 50 it was 60%-15% lower for females compared with males. Mean femur neck BMD was 5%-13% lower for females than males in all age groups except 12-15.