Lumbar Spine Bone Mineral Density Predictive of Fracture Among Women Transitioning to Menopause

Both premenopausal and postmenopausal bone mineral density (BMD) and rate of BMD decline in the lumbar spine were found to be independent risk factors for fracture, according to the results of a longitudinal cohort study published in the Journal of Clinical Endocrinology and Metabolism.

Women (N=451) aged 42 to 52 years were recruited from 7 centers in the United States to participate in the SWAN study in 1996. Study participants were assessed every 18 months for lumbar spine and femoral neck BMD. Researchers from the University of California Los Angeles analyzed these data for associations between demographic and clinical characteristics with risk of fracture.

Participants were White (40%), Black (31%), Japanese (16%), and Chinese (13%); mean BMI was 28.3 kg/m²; and women began BMD assessment 1.7 years prior to their final menstrual period. At baseline, BMD at the lumbar spine was 1.075 g/cm² and at the femoral neck was 0.848 (SD, 0.128) g/cm².

Early in postmenopause (mean, 6.7 years), BMD decreased to 0.966 g/cm² at the lumbar spine and 0.767 g/cm² at the femoral neck. These declines correlated with a rate of decline of 1.5% at the lumbar spine and 1.3% at the femoral neck.

A minority of women (n=34) sustained a postmenopausal fracture at an average time to first fracture of 6.8 years. Fractures occurred at the wrist, ankle, foot, leg, arm, ribs, spine, hip, and shoulder; 35% of fractures were assessed as traumatic. Fractures occurred most frequently among White women (51%), followed by Black women (31%), Chinese women (13%), and Japanese women (5%).

Incident fracture was associated with 1 standard deviation decrease in baseline lumbar spine BMD (adjusted hazard ratio [aHR], 1.78; 95% CI, 1.17-2.72; P =.0007) and 1% faster decline in lumbar spine BMD (aHR, 1.56; 95% CI, 1.02-2.41; P =.04). Femoral BMD was not significantly associated with incident fracture. Patients who had low baseline lumbar spine BMD and fast decline were at greatest risk for fracture (HR, 2.73; 95% CI, 1.05-7.08; P =.03).

This study may have been limited by including both traumatic and atraumatic fractures; however, all fracture types were included as there was a low fracture incidence rate. The study data indicated that the premenopausal lumbar spinal BMD and postmenopausal rate of decline were better predictors of fractures among women transitioning to menopause.

Reference

Shieh A, Karlamangla AS, Huang M-H, Han W, Greendale GA. Faster lumbar spine bone loss in midlife predicts subsequent fracture independent of starting bone mineral density. J Clin Endocrinol Metab. Published online April 27, 2021. doi:10.1210/clinem/dgab279