Geometric indices of bone strength are associated with physical activity and dietary calcium intake in healthy older women

Michelle K. Nurzenski, N. Kathryn Briffa, Roger I. Price, Benjamin C.C. Khoo, Amanda Devine, Thomas J. Beck, Richard L. Prince

Research output: Contribution to journalArticlepeer-review

Abstract

A population-based study on 1008 postmenopausal women identified that the 24% of women achieving high levels of PA and CI had 3.4-4.4% higher femoral bone strength in axial compression and 1.7-5.2% in bending than those achieving low levels, indicating that lifestyle factors influence bone strength in the proximal femur. Introduction: Extensive research has shown that increased physical activity (PA) and calcium intake (CI) decrease the rate of bone loss; however, there is little research on how these lifestyle variables affect bone geometry. This study was designed to investigate the effects of modifiable lifestyle variables, habitual PA and dietary CI, on femoral geometry in older women. Materials and Methods: Femoral geometry, habitual PA, and dietary CI were measured in a population-based sample of 1008 women (median age ± interquartile range, 75 ± 4years) enrolled in a randomized controlled trial (RCT) of calcium supplementation. Baseline PA and CI were assessed by validated questionnaires, and 1-year DXA scans (Hologic 4500A) were analyzed using the hip structural analysis technique. Section modulus (Z), an index of bending strength, cross-sectional area (CSA), an index of axial compression strength, subperiosteal width (SPW), and centroid position, the position of the center of mass, were measured at the femoral neck (NN), intertrochanter (TT). and femoral shaft (FS) sites. These data were divided into fertiles of PA and CI, and the results were compared using analysis of covariance (ANCOVA), with corrections for age, height, weight, and treatment (calcium/placebo). Results and Conclusions: PA showed a significant dose-response effect on CSA all hip sites (p < 0.03) and Z at the narrow neck and intertrochanter sites (p < 0.02). For CI, there was a dose-response effect for centroid position at the intertrochanter (p = 0.03). These effects were additive, such that the women (n = 240) with PA in excess of 65.5 kcal/day and CI in excess of 1039 mg/day had significantly greater CSA (NN, 4.4%: IT, 4.3%; FS, 3.4%) and Z (NN, 3.9%; IT, 5.2%). These data show a favorable association between PA and aspects of bone structural geometry consistent with better bone strength. Association between CI and bone structure was only evident in 1 of 15 variables tested. However, there was evidence that there may be additive effects, whereby women with high levels of PA and CI in excess of 1039 mg/day had significantly greater CSA (NN, 0.4%; FS, 2.1%) and Z (IT, 3.0%) than women with high PA but low CI. These data show that current public health guidelines for PA and dietary CI are not inappropriate where bone structure is the health component of interest.

Original languageEnglish (US)
Pages (from-to)416-424
Number of pages9
JournalJournal of Bone and Mineral Research
Volume22
Issue number3
DOIs
StatePublished - Mar 2007

Keywords

  • Aging
  • Bone
  • Calcium intake
  • Hip structural analysis
  • Physical activity

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Orthopedics and Sports Medicine

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