Determinants of bone mineralization in 8 to 20 year old Finnish females

Abstract

OBJECTIVES: To study the determinants of bone mass and density in Finnish girls and young women.

DESIGN: A cross-sectional study.

SUBJECTS: One hundred and seventy six 8 to 20 year old female volunteers living in the city of Tampere, Finland.

METHODS: Calcium intake was estimated from a 7 d calcium intake diary (CaD). Bone mineral content (BMC) and areal density (BMD) were measured by dual-energy X-ray absorptiometry (DXA) at the lumbar spine, femoral neck and distal radius. Volumetric bone mineral apparent density (BMAD) was estimated from these DXA data. In addition, anthropometric characteristics, isometric muscle strength, and the Tanner stage were determined. Menstrual status and physical activity level were assessed by a questionnaire and personal interview.

RESULTS: Body weight and Tanner stage were the most important determinants of BMC and BMD. Physical activity was the only not growth-related factor associated with BMC, BMD and BMAD. Therefore, it was examined in detail between the PA and NA groups. Site-specific benefits varied from 5–7% for the BMC (lumbar spine and radius) and BMD (lumbar spine and femoral neck) and was about 5% for the BMAD (femoral neck).

CONCLUSIONS: Body weight seems to be the most important determinant of the BMC and BMD of growing Finnish girls, but during puberty exercise may beneficially affect BMD at the loaded skeletal sites. Exercise may increase femoral BMAD during peripubertal years. There was no association between calcium intake and the bone variables, but the high level so calcium intake in all age groups of the study was likely to explain the lack of association.