Bone mineral density in postmenopausal Caucasian, Filipina, and Hispanic women.

Background: Previous bone mineral density (BMD) studies have suggested Asian women have lower BMD and Hispanic women have similar or higher BMD compared with Caucasian women, partially explained by ethnic differences in body size. This study compared the effect of different variables representing body size on BMD in postmenopausal women aged 50-69 years from three ethnic groups in San Diego County, CA: 354 Caucasians, 285 Filipinas, and 164 Hispanics.

Methods: In all three groups, BMD was measured by DXA (Hologic 2000) at the hip, lumbar spine, and total body. Lifestyle variables and anthropometric measures were assessed by standard methodology; medication and supplement use were validated by a nurse.

Results: Regardless of the variables used to represent body size in the regression modelling, either body mass index or lean and fat tissue mass, ethnic differences were minimal across the three groups. The only significant differences observed using the two fully adjusted models (age, height, body mass index or lean and fat tissue mass, smoking, alcohol, exercise, current oestrogen and calcium supplement use, and osteoarthritis) were at the total body BMD site where Filipinas had significantly higher BMD than the Caucasians or Hispanics, whose total body BMD was similar to one another. The independent variables in the fully adjusted models explained approximately 20-40% of the variation in BMD at each of the four sites. Income or occupation did not help explain BMD differences, but a pattern of increased BMD among those with some college education in all three groups was observed.

Conclusions: Accounting for body size using either body mass index or fat and lean tissue mass along with height and other lifestyle variables minimizes ethnic differences and explains a considerable amount of variation in mean BMD among older ethnic minority and Caucasian women.