Determinants of lumbar bone mineral density in normal weight, non-smoking women soon after menopause. A study using clinical data and quantitative computed tomography

OBJECTIVES: Is there an influence of oral contraceptive use, parity and lactation on early postmenopausal bone mass? Is assessment of reproductive history, body weight in combination with biochemical markers of bone metabolism suitable to predict lumbar bone mass soon after menopause?

STUDY DESIGN: A cross-sectional study in 94 healthy, normal weight, non-smoking women, 1-3 years after spontaneous menopause. Bone mineral density (BMD) of the lumbar spine was measured with single energy quantitative computed tomography.

RESULTS: Multiple regression analysis showed that only total duration of lactation and alkaline phosphatase (AP) levels are independently related to trabecular BMD (P = 0.001 and P = 0.002 respectively). AP was also associated with cortical BMD (P = 0.003). Assessment of reproductive history, body mass index and biochemical markers of bone metabolism could only account for 17% of the variation of trabecular BMD observed in the study population.

CONCLUSION: This study suggests that total duration of lactation rather than parity is associated with trabecular BMD of the spine. Clinical assessment of risk factors unsuccessfully predicts lumbar BMD in healthy, early postmenopausal women.