Although early menopause is linked to increased risks in bone loss and fracture, new research indicates that, even among the majority of women who have menopause after age 45, the time since the final menstrual period can be a stronger predictor than chronological age for key risks in bone health and fracture.
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In a large longitudinal cohort, the number of years since a woman’s final menstrual period specifically showed a stronger association with femoral neck bone mineral density (BMD) than chronological age, while an earlier age at menopause – even among those over 45 years, was linked to an increased risk of fracture.
“Most of our clinical tools to predict osteoporosis-related outcomes use chronological age,” first author Albert Shieh, MD, told this news organization.
“Our findings suggest that more research should be done to examine whether ovarian age (time since final menstrual period) should be used in these tools as well.”
An increased focus on the significance of age at the time of the final menstrual period, compared with chronological age, has gained interest in risk assessment because of the known acceleration in the decline of BMD that occurs 1 year prior to the final menstrual period and continues at a rapid pace for 3 years afterwards before slowing.
To further investigate the association with BMD, Dr. Shieh, an endocrinologist specializing in osteoporosis at the University of California, Los Angeles, and his colleagues turned to data from the Study of Women’s Health Across the Nation (SWAN), a longitudinal cohort study of ambulatory women with pre- or early perimenopausal baseline data and 15 annual follow-up assessments.
Outcomes regarding postmenopausal lumbar spine (LS) or femoral neck (FN) BMD were evaluated in 1,038 women, while the time to fracture in relation to the final menstrual period was separately evaluated in 1,554 women.
In both cohorts, the women had a known final menstrual period at age 45 or older, and on average, their final menstrual period occurred at age 52.
After a multivariate adjustment for age, body mass index, and various other factors, they found that each additional year after a woman’s final menstrual period was associated with a significant (0.006 g/cm2) reduction in postmenopausal lumbar spine BMD and a 0.004 g/cm2 reduction femoral neck BMD (both P < .0001).
Conversely, chronological age was not associated with a change in femoral neck BMD when evaluated independently of years since the final menstrual period, the researchers reported in the Journal of Clinical Endocrinology and Metabolism.
Regarding lumbar spine BMD, chronological age was unexpectedly associated not just with change, but in fact with increases in lumbar spine BMD (P < .0001 per year). However, the authors speculate the change “is likely a reflection of age-associated degenerative changes causing false elevations in BMD measured by dual-energy x-ray absorptiometry.”
Fracture risk with earlier menopause
In terms of the fracture risk analysis, despite the women all being aged 45 or older, earlier age at menopause was still tied to an increased risk of incident fracture, with a 5% increase in risk for each earlier year in age at the time of the final menstrual period (P = .02).