The effects of menopause on longitudinal bone loss from the spine.

Two hundred and thirty women aged 45-66 years were divided into three groups according to their menopausal status and were followed to assess the changes in vertebral bone mineral density (BMD). These included 71 premenopausal, 42 perimenopausal, and 117 postmenopausal women. Menopausal status was assessed through menstrual history and plasma concentrations of 17 beta estradiol and luteinizing hormone. BMD was measured by dual photon absorptiometry between 2 and 5 times over an average period of 27 months, and annual rates of changes were calculated by linear regression. BMD decreased significantly (P < 0.0001) in the three groups during the follow-up. Mean (+/- SD) annual rate of change was -0.79 +/- 1.5% for premenopausal, -2.35 +/- 1.5% for perimenopausal, and -1.24 +/- 1.5% for postmenopausal women. There was no difference in the rates of bone loss between the perimenopausal group and the postmenopausal group within 3 years after menopause (1-2 years: -2.34 +/- 2.1%; 2-3 years: -1.9 +/- 1.5%). Thereafter, rates decreased exponentially with time since menopause to fall out at the same level as the premenopausal level. These longitudinal data indicate that vertebral bone loss begins before menopause and accelerates sharply during menopause to decline exponentially with time after 3 years.