Bone loss in relation to menopause: a prospective study during 16 years

This prospective study evaluated bone loss in the peri- and postmenopausal period in 156 women followed from age 48 to 64 years. All women were premenopausal at the start of the study. Areal bone mineral density (g/cm(2)) was measured by single-photon absorptiometry (SPA) of the forearm at the 1 cm level (BMD 1 cm) and the 6 cm level (BMD 6 cm) every second year. Onset of menopause (MP) was determined according to the criteria of the World Health Organization (12 months of amenorrhea and elevated follicle-stimulating hormone). At the end of the study, 125 of 156 women (80%) remained. Bone mineral density (BMD) at age 48 years correlated with BMD at age 64 years within the respective region (r = 0.4-0.5, p < 0.001, respectively). There was no BMD loss in the premenopausal period. BMD loss was accelerated at menopause (MP) independent of chronological age. BMD loss was greater during the first 5 years following MP than during the following 6 years (BMD 1 cm 2.4% per year [1.0%-3.9%] vs. 0.4% per year [-0.3%-1.0%], p < 0.01). The quartile of women with late MP (>53.7 years) had greater bone loss during the first 5 years after MP than the quartile of women with early MP (<50.3 years) (p < 0.001). At age 64 years, BMD was no different when comparing the quartile of women with late MP vs. the quartile of women with early MP. Furthermore, there was no correlation between age at menopause and BMD at the age of 64. In summary, among women still menstruating at age 48 years, there was no measurable BMD loss in the premenopausal period. Independent of chronological age, BMD loss accelerated during MP. Rates of loss were highest in the early postmenopausal period. Independent of age at MP, premenopausal women with low age-specific BMD at age 48 years had an increased risk of sustaining low BMD at age 64 years also.