Journals of Gerontology Series A: Biological Sciences and Medical Sciences, Vol 52, Issue 6 M337-M342, Copyright © 1997 by The Gerontological Society of America
Determinants of bone mineral density in postmenopausal white Iowans
MC Willing, JC Torner, TL Burns, ET Segar and JR Werner
Department of Pediatrics, College of Medicine, University of Iowa, USA. [email protected]
BACKGROUND: Osteoporosis is a major health problem for older individuals.
For women, development of osteoporosis is a function of the accretion of
"peak" bone mass in the third decade, age at menopause, and rate of bone
loss with aging. Low bone mineral density (BMD) is a major risk factor for
osteoporosis and fracture. The purpose of this study was to identify life
style, nutritional, medical, and genetic predictors of low BMD in
postmenopausal Iowa women. METHODS: One hundred thirty-four postmenopausal
White women ranging in age from 57 to 81 years were included in this
case-control study. Bone mineral density was measured at the femoral neck,
using dual photon X-ray absorptiometry (Hologic 2000 QDR). Sixty-six women
with BMD measurements below 0.68 g/cm2 (the bottom quartile of the BMD
distribution in the population from which participants were recruited), and
68 women with values at or above 0.83 g/cm2 (the top quartile of the BMD
distribution in the same population) were included. Information about
environmental, nutritional, medical, and life style modifiers of BMD was
obtained by written questionnaire and telephone interview. To assess
familial factors that might influence BMD, we obtained a detailed family
history for each participant. In addition, we tested the hypothesis that
allelic variation at the Vitamin D receptor (VDR), and the type I collagen
gene (COL1A1 and COL1A2) loci influence BMD. RESULTS: Weight, loss of
height, age, and age at menopause were strong predictors of BMD in our
population. After adjustment for these differences, we found no effect of
genotype at the COL1A1, COL1A2, and VDR loci on BMD. CONCLUSIONS: Bone
mineral density is a complex trait that is influenced by several different
modifiers; in the present study, weight was the best predictor of
postmenopausal BMD. While several studies suggest that VDR genotype is an
important determinant of BMD, we did not find this association in our
population, nor did we identify an association between allelic variation at
the type I collagen gene loci and BMD. Identification of genes that
determine body mass index may provide additional insight into risk factors
for low BMD, and osteoporotic fractures.
