BMDs Derived From Total Body DXA are Strongly Correlated With Dedicated Hip and Spine BMD and are Associated With Prior Fractures in NHANES

Dedicated dual energy X-ray absorptiometry (DXA) bone mineral density (BMD) of the hip and spine are strongly associated with fractures, but it is not clear whether total body (TB) DXA measures correlate with dedicated DXA or relate to fractures. Using National Health and Nutrition Examination Survey (NHANES) data from years 2013-2014 and 2017-2018, we assessed Pearson correlations between dedicated and TB DXA measures. Associations with fractures were examined using self-reported prior fractures or fractures found on vertebral fracture assessment (VFA) using logistic regression models while controlling for age, gender, race/ethnicity, and body mass index. Among 1418 subjects from NHANES 2013-2014, we found signification correlations between all dedicated DXA BMD and TB DXA BMD measures. For dedicated spine BMD, the TB site with the strongest correlation was TB lumbar spine (r = 0.87, p < 0.001), while for dedicated total hip and femoral neck BMD, total body, pelvis, leg, and trunk BMD had the strongest correlations (r = 0.67-0.75, p < 0.001 for all). There were relatively few differences by sex or race/ethnicity. Findings were similar in 481 subjects from NHANES 2017-2018. In NHANES 2013-2014, there were 438 prior fractures in 370 subjects (26.3%). When controlling for age, gender, race/ethnicity, and body mass index, the adjusted odds ratio for fracture per T-score decrease of BMD were similar for TB BMD measures as for dedicated BMD measures (OR 1.10-1.28). In conclusion, total body DXA measures are correlated with hip and spine DXA and are strongly associated with prior fracture. Our results suggest that total body DXA measures are valid alternative sites to study BMD and fracture risk.