D-14I Free Communication/Poster Assessment of Body Composition
The diagnosis of osteoporosis is based on the assessment of bone mineral density (BMD). BMD recorded at the hip is regarded as the gold standard, since it has the highest predictive value of hip fracture, the most severe complication of osteoporosis.
To determine whether the BMD recorded from one skeletal site will reflect the BMD recorded at other sites.
BMD recorded at 10 skeletal sites throughout the body of 49 female endurance runners (30.8 ± 5.6 yrs) was used to assess the intersite correlations. Factor analysis with Varimax rotation was used to determine the minimum number and nature of the components necessary to describe these correlations.
All intersite correlations were significant (p < 0.05) with the exception of those between the left arm and left rib, thoracic spine and pelvis. The greatest correlations were observed between the right and left legs (r=0.89) followed by the right and left ribs (r=0.88). The factor analysis suggested a two-factor solution, i.e. the 10 skeletal-site BMD variables were reduced to just two new (latent) variables or components. The loadings indicated an upper (ribs, right arm, thoracic spine, lumber spine and pelvis) and a lower body (right leg, left leg and hip) component. Together, these two components explained 71% of the original variance with 59% being associated with the new upper body and 12% with the new lower body component. Interestingly, the left arm failed to identify strongly with either component, with hip and thoracic spine loading moderately on both.
Within this population of female runners, there is a serious danger of misclassification when using BMD recorded at lower body skeletal sites to assess the risk of osteoporosis at upper body sites, and vice-versa.