Changes in femur neck bone density in US adults between 1988–1994 and 2005–2008: demographic patterns and possible determinants

Summary This analysis compares femur neck bone mineral density (FNBMD) and bone determinants in adults between National Health and Nutrition Examination Survey (NHANES) III (1988.1994) and NHANES 2005.2008. FNBMD was higher in NHANES 2005.2008 than in NHANES III, but between-survey differences varied by age, sex, and race/ethnicity. The likelihood that FNBMD has improved appears strongest for older white women. Introduction Recent data on hip fracture incidence and femur neck osteoporosis suggest that the skeletal status of older US adults has improved since the 1990s, but the explanation for these changes remains uncertain. Methods The present study compares mean FNBMD of adults ages 20 years and older between the third (NHANES III, 1988.1994) and NHANES 2005.2008. Dual-energy Xray absorptiometry systems (pencil beam in NHANES III, fan beam in NHANES 2005.2008) were used to measure hip BMD, and several bone determinants are compared between surveys to assess their potential role in explaining observed FNBMD differences. Results FNBMD was higher overall in NHANES 2005. 2008 than in NHANES III, but between-survey differences varied by age, sex, and race/ethnicity. Although FNBMD differences in several groups were small enough (.3%) to be attributable to use of different dual-energy X-ray absorptiometry (DXA) systems in the two surveys, variability in size and direction of the differences does not support artifactual differences in DXA methodology as the sole explanation. Several FNBMD determinants (body size, smoking, selected bone-active medications, self-reported health status, calcium intake, and caffeine consumption) changed in a bone-improving direction in older adults, but FNBMD in older non-Hispanic white women remained significantly higher in 2005.2008 even after adjusting for DXA methodology or for the selected bone determinants. Conclusion The likelihood that FNBMD has improved appears strongest for older white women, but the reason for the improvement in this group remains unclear.