Post-menarcheal Trabecular Bone Score as a Function of Organized Physical Activity

Abstract

PURPOSE: Trabecular bone score (TBS) grades lumbar spine trabecular texture based on DXA scan gray level variation. In adults, TBS correlates with trabecular density indices and predicts fracture risk, independent of areal bone mineral density (BMD). However, few pediatric studies have evaluated TBS, with none demonstrating significant exercise loading associations. Bone accrual accelerates circum-menarche; thus, we hypothesized that circum-menarcheal organized physical activity (OPA, h/wk) would correlate with post-menarcheal TBS, suggesting potential for improvement of baseline adult trabecular texture via circum-menarcheal exercise. METHODS: Annual DXA scans and semi-annual OPA records were collected via a prospective, longitudinal study of exercise and bone accrual. Analysis inclusion criteria were: 1) a postero-anterior lumbar spine DXA scan (Hologic, Waltham MA) from 0-1 year post-menarche; 2) prior year OPA records. Raw TBS data were generated using proprietary TBS iN-sight software (v2.2, Medimaps, France), adjusted for pediatric-specific soft-tissue effects. Multiple regression evaluated linear and quadratic associations between prior year OPA and TBS, accounting for gynecological age; β and significance are reported for each predictor. To reduce variance inflation, the quadratic function was mean-centered. RESULTS: Data were included for 111 girls, with means as follows: age 13.4 yrs (10.0 to 15.6, sd 1.1), age at menarche 12.9 yrs (sd 1.1), gynecological age 0.5 yrs (sd 0.3), OPA 8.0 h/wk (sd 5.8) and TBS 1.38 (1.15 to 1.58, sd 0.08). In a regression model entering OPA, OPA2 and gynecological age, a significant non-linear association was observed with OPA (respective β= 0.003, -0.001, 0.043, p=0.08, 0.003, 0.12). CONCLUSIONS: Our data suggest a target circum-menarcheal OPA range of 5 to 15 h/wk. Further research is needed to confirm that TBS is modifiable via pediatric exercise to optimize baseline adult trabecular texture.