Skin color and body size as risk factors for osteoporosis

We compared skin color, body size and bone mineral density (BMD) among three groups of postmenopausal women: 104 healthy black women, 45 healthy white women, and 52 osteoporotic white women with vertebral fractures. Skin color was measured by reflectometry, stature with a Harpenden stadiometer, weight with digital scales, and radial BMD by single photon absorptiometry. There were no significant differences in mean skin color (age-adjusted) between the healthy and osteoporotic white women, although both white groups differed from the black group. There was no significant correlation between skin color and BMD (age- and weight/height-adjusted) in any of the groups. All three groups differed significantly in age-adjusted BMD, although there was less difference between the healthy blacks and whites when covariates (body size, age) were taken into account. We further investigated body size differences by estimating stature at age 55 in all three groups based on our observations that osteoporotic women with vertebral fractures lose height at a rate that is 2.6 times faster than that of healthy aging women. Our analyses indicate that the osteoporotics were not shorter than the normals before the onset of their disease (based on estimated height), and do not have a significantly smaller body mass (weight/height and weight/height 2) than the normal white women. Additionally, the osteoporotics are above the ideal body mass index recommended by the National Institutes of Health. We conclude that fair skin is not a risk factor for osteoporosis and that large body size is not protective against the development of osteoporosis, although it may have a salutary effect on BMD in both blacks and whites.