Bone mineral density in normal Swedish women

We examined 429 women, aged 20–80 years, randomly selected from the population register to establish normal values for bone mineral density (BMD) in Swedish women. BMD of the spine and hip was measured by dual-energy X-ray absorptiometry (DEXA; Hologic QDR 1000) and in the forearm by single photon absorptiometry (SPA; Molsgaard ND-1100). The recalled age of menarche was negatively correlated to BMD at all ages. There was no significant change in BMD from 20–49 years at any site except a slight decline at Wardʹs triangle. Bone loss was rapid at all sites during the first decade after menopause. Thereafter, BMD declined slowly in the trochanter and total hip but more rapidly in the forearm, femoral neck, and Wardʹs triangle. BMD in the spine even increased in the eighth decade probably due to osteoarthritis. The average change in forearm BMD during the 15 perimenopausal years comprising mean age for menopause ± 2 SD (43–57 years) was −0.4% per year in premenopausal females and −1.6% per year in postmenopausal females. The corresponding annual percental change was, for the spine, +0.2 and −1.7; neck, −0.7 and −1.7; trochanter, +0.5 and −1.5; and Wardʹs triangle, −0.1% and −2.2%, respectively. Our normal values for lumbar spine BMD prior to menopause did not differ from published values or the manufacturerʹs normal values; however, our spine BMD values for the first decade after menopause were significantly lower (≈10%) than in other studies. Our femoral neck BMD values for younger women were, like those of several other groups, significantly lower than the manufacturerʹs normal values, but our sample of young women in this study was small. The prevalence of osteoporosis, if defined as t score < −2.5 is highly dependent on the sampling of the reference population of young adult women, and also on the choice of skeletal site. Further studies on bone mineral density in healthy young adult women are needed.