Age-specific reference values for lumbar spine trabecular bone score (TBS) in Brazilian adult women

OBJECTIVE: To evaluate age-related changes in lumbar spine trabecular bone microarchitecture using the trabecular bone score (TBS) and to establish age-specific reference values for healthy Brazilian women. METHODS: In this cross-sectional study, we evaluated 527 healthy adult women aged 20-82 years recruited as a convenience sample from hospital employees and their relatives. Lumbar spine TBS and bone mineral density (BMD) were obtained from a Hologic Discovery A DXA system using TBS iNsight software (v3.0.3). Primary analyses were restricted to BMI 15-37 kg/m2 and excluded current menopausal hormone therapy users, with sensitivity analyses including these participants. Women were stratified by age decade; menopause-centered analyses were additionally performed using years since menopause, and nonlinearity was explored using restricted cubic splines. RESULTS: In the primary analytical sample (n=477), TBS was independently associated with age after adjustment for height and weight (β=-0.004 per year, P<0.001). Among postmenopausal women, years since menopause was independently associated with lower TBS (β=-0.002 per year, P=0.010). Menopausal status and the age-by-menopausal status interaction were not independently associated with TBS. TBS declined earlier across age decades than BMD T-scores, and sensitivity analyses including hormone therapy users yielded similar results. Using the reference distribution from premenopausal women aged 20-39 years, TBS cutoffs were 1.365 for normal microarchitecture and 1.248 for degraded microarchitecture, with intermediate values indicating partially degraded microarchitecture. A substantial proportion of women with normal BMD showed impaired trabecular microarchitecture by TBS, ranging from 34.8% to 41.6% across skeletal sites. CONCLUSIONS: This study provides the first age-specific normative TBS reference data for Brazilian women. The findings indicate that trabecular microarchitecture deteriorates earlier and more rapidly with aging than bone mass loss captured by BMD, supporting the use of TBS as a complementary tool for evaluating skeletal health and fracture risk.