Abstract
CONTEXT: Previous studies of menopausal age and length of reproductive life on bone are limited by retrospective reproductive histories, being cross-sectional, or lacking gold standard bone technologies or information on hormone replacement therapy (HRT) or surgical treatment. OBJECTIVE: The objective of the study was to investigate age at menopause, length of reproductive life, and HRT use in relation to volumetric and areal bone mineral density (vBMD, aBMD), bone size, and strength in women aged 60-64 years. DESIGN: This was a birth cohort study that followed up for 64 years with prospective measures of age at menarche and menopause and monthly HRT histories. SETTING: The study was conducted in England, Scotland, and Wales. PARTICIPANTS: Participants included 848 women with a known type of menopause and bone measures at 60-64 years. MAIN OUTCOME MEASURES: Peripheral quantitative computed tomography measurements of the distal radius total and trabecular vBMD were measured. Diaphyseal radius total and medullary cross-sectional area, cortical vBMD, and polar strength strain index (SSI); dual-energy x-ray absorptiometry measurements of aBMD at the lumbar spine and total hip were also measured. RESULTS: A 10-year increase in age at natural (but not surgical) menopause was associated with 8.2% (95% confidence interval [CI] 1.3%-15.1%, P = .02) greater trabecular vBMD and a 6.0% (95% CI 0.51%-11.5%, P = .03) greater total vBMD; findings were similar for length of reproductive life. A 10-year difference in HRT use was associated with a 6.0% (95% CI 2.6%-9.3%, P < .001) greater polar SSI and a 0.9% (95% CI 0.4%-1.5%, P = .001) greater cortical vBMD. These estimates changed little on adjustment. Estimates for aBMD were consistent with those for peripheral quantitative computed tomography. CONCLUSIONS: The positive effects on trabecular vBMD of later natural menopause and longer reproductive life persisted into early old age. HRT use was associated with greater radius cortical vBMD and polar SSI and aBMD.