Association and relative importance of multiple obesity measures with bone mineral density: the National Health and Nutrition Examination Survey 2005-2006

All obesity measures were positively associated with femoral neck bone mineral density (BMD), but not with lumbar spine BMD. Hip circumference was the most important obesity measure in relation to BMD. Purpose Multiple measures are used to quantify obesity; different obesity measures have diverse relationship with BMD. Which obesity measure has the most important value in relation to BMD is still poorly understood. We examined the association between multiple obesity measures and BMD and determined the relative importance (RI, percentage of variation) of multiple obesity measures associated with BMD. Methods Data from 5287 men and women aged between 8 and 69 years (mean age=29 years) in the National Health and Nutrition Examination Survey 2005-2006 were analyzed. Body mass index (BMI), waist circumference, hip circumference, body fat mass (FM) index, total body FM, abdominal FM, and appendicular FM were considered the exposures and femoral neck and lumbar spine BMD the outcomes. Results In the multivariable analysis, greater BMI and hip circumference were associated with increased BMD at the lumbar spine and femoral neck (all P<0.001). The remaining obesity variables were positively associated with increased femoral neck BMD only (all P<0.001). RI of all obesity measures associated with femoral neck BMD was much greater than that associated with lumbar spine BMD. Moreover, hip circumference had higher RI (19.8 for femoral neck BMD; 7.0 for lumbar spine BMD) than other obesity measures (all RIs <= 14.1 for femoral neck BMD; all RIs <= 3.5 for lumbar spine BMD) in relation to BMD. Conclusions All obesity measures were positively associated with femoral neck BMD, but not with lumbar spine BMD. Hip circumference was the most important obesity measure in relation to BMD.