Associations between Body Composition, Hormonal and Lifestyle Factors, Bone Turnover, and BMD.
BACKGROUND
The relative importance of body composition, lifestyle factors, bone turnover and hormonal factors in determining bone mineral density (BMD) is unknown. We studied younger postmenopausal women to determine whether modifiable or nonmodifiable risk factors for osteoporosis have stronger associations with BMD.


METHODS
In multivariable linear regression models, we tested associations between non-bone body composition measures, self-reported measures of physical activity and dietary intake, urinary N-telopeptide (NTx), sex hormone concentrations, and BMD in 109 postmenopausal women aged 50 to 64 years, adjusting for current hormone therapy use and clinical risk factors for low BMD. Lean mass, fat mass and areal BMD (aBMD) at the lumbar spine, femoral neck, total hip and distal radius were measured using dual energy X-ray absorptiometry.


RESULTS
Higher body weight and self-reported nonwhite race were independently associated with higher aBMD at the lumbar spine, femoral neck, total hip and distal radius. Lean and fat mass were not independently associated with aBMD. Older age and higher urinary NTx were independently associated with lower aBMD at the distal radius but not at weight-bearing sites. Sensitivity analyses demonstrated lack of an independent association between total daily protein or calorie intake and BMD.


CONCLUSIONS
BMD, weight and race were the most important determinants of aBMD at all sites. Older age and higher bone turnover were independently associated with lower aBMD at the distal radius. In a limited analysis, self-reported physical activity, dietary protein and calorie intake were not associated with aBMD after adjustment for the other variables.
Department of Family Medicine, University of North Carolina, Chapel Hill, NC, USA.
Margaret L
ML
Gourlay
Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC, USA.
Catherine A
CA
Hammett-Stabler
Department of Radiology, University of North Carolina, Chapel Hill, NC, USA.
Jordan B
JB
Renner
Department of Medicine and Division of Endocrinology, University of North Carolina, Chapel Hill, NC, USA.
Janet E
JE
Rubin
Body weight; Bone density; Life style; Menopause; Osteoporosis; Postmenopausal