Bone mineral density in older non-Hispanic Caucasian and Mexican-American women: relationship to lean and fat mass.
OBJECTIVE
The prevalence of osteoporotic fracture is higher in non-Hispanic Caucasian (NHC) than Mexican-American (MA) women in the USA. The present study examined bone mineral density (BMD) in these two ethnic groups and the association between BMD and body composition.


METHODS
Cross-sectional.


METHODS
Sixty-two NHC and 54 MA women, aged 60-86 years, with a body mass index (kgm(-2)) of <30.


METHODS
BMD (gcm(-2)) of the spine (L2-4), hip (femoral neck, trochanter, Ward's triangle) and whole body was determined by dual-energy X-ray absorptiometry (DXA). Bone mineral-free lean mass (LM) and fat mass (FM) and several ratios of body fat distribution were also assessed by DXA.


RESULTS
There was no difference in age (NHC, 69.5+/-0.7; MA 69.5+/-0.9 years; mean +/- SEM) or body mass, but MA women were shorter with a higher truncal adiposity (p < 0.001). There was no significant difference in BMD between groups, however, adjusting for height resulted in higher hip and whole body BMD in MA women (p < 0.01). When volumetric bone density was calculated (bone mineral apparent density; BMAD, gcm(-3)), a trend for higher values in MA women was observed at the femoral neck (p = 0.018). LM contributed independently to BMD at the spine and hip in NHC women, with FM also contributing at the femoral neck. In MA women, LM was an independent contributor to lumbar spine and trochanter BMD, and both LM and FM contributed to whole body BMD. However, the effects of LM and FM were removed in both groups when BMD was adjusted for body or bone size, the only exception being at the trochanter in NHC women.


CONCLUSIONS
These results indicate that MA women have higher bone density at the proximal femur than NHC women, which may partially account for their lower rate of hip fracture. Further, differences in bone density between the two ethnic groups do not appear to be dependent on soft-tissue composition.
Taaffe
D R
DR
The Aging Study Unit, Palo Alto, California, USA. taaffed@exmur.nia.nih.gov
Villa
M L
ML
Holloway
L
L
Marcus
R
R
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism; D001823:Body Composition; D015519:Bone Density; D002784:Cholesterol / Q000378:metabolism; D003430:Cross-Sectional Studies; D005223:Fats / Q000378:metabolism*; D005260:Female; D005269:Femur / Q000502:physiology; D005272:Femur Neck / Q000502:physiology; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008159:Lumbar Vertebrae; D017058:Mexican Americans; D014280:Triglycerides / Q000378:metabolism; D044465:White People
D005223:Fats; D018972:Insulin-Like Growth Factor Binding Protein 3; D014280:Triglycerides; D007334:Insulin-Like Growth Factor I; D002784:Cholesterol