Bone mineral density in pre-professional female ballet dancers: a systematic review and meta-analysis

Objectives: To quantitatively compare bone mineral density (BMD) outcomes between pre-professional female adolescent ballet dancers and control populations.
Design: Systematic review and meta-analysis.
Methods: Six electronic databases and relevant journals were systematically searched up to August 2017. Included articles examined BMD in adolescent females undergoing pre-professional ballet training and healthy age-matched controls with an available English full text. Dancers were aged 15–19 years and trained in ballet at least 10 h per week. BMD data were analysed via standardized mean difference to account for differences in reporting methods
Results: From 3984 potential articles, 8 cross-sectional studies were accepted for inclusion, which compared 293 dancers (16.9 ± 0.8 years) to 333 controls (16.9 ± 0.9 years). No data were available from longitudinal studies. Dancers displayed lower BMD at the radius and higher BMD at the femoral neck, femoral trochanter and Ward’s triangle. No significant differences were observed in the lumbar spine or tibia. The overall study quality was low and heterogeneity was present in some analyses.
Conclusions: This meta-analysis indicates that there may be a site-specific osteogenic effect of pre-professional classical ballet training in adolescent females, with a notable and concerning finding of reduced upper limb BMD compared to age-matched controls. Longitudinal cohort studies are required to confirm the effects of pre-professional ballet training on BMD during adolescence.