Bone Mineral Density Differences between Adolescent Dancers and Non-exercising Adolescent Females

Study Objective To compare the bone mineral density (BMD) of the axial and appendicular skeleton between regularly exercising collegiate dancers and age matched non-exercising young females between the age of 17 and 19 to assess the impact of weight-bearing exercises and menstrual status on BMD. Design Prospective observational cohort. Setting Sports clinic in a collegiate school of dance and a hospital-based adolescent clinic. Participants The adolescent dancers consisted of full-time collegiate dance students from a tertiary Performing Arts Institute (n = 35). The non-exercising controls consisted of eumenorrhoeic patients of the same age presenting to the Adolescent Clinic (n = 35). Interventions All subjects had a full hormonal profile, bio-impedance estimation of body fat, and dual energy X-ray absorptiometry and quantitative peripheral CT scans (pQCT) to determine bone density. Main outcome measures Comparison of the mean bone mineral density in the axial and appendicular skeleton between the two groups. Results The incidence of oligo/amenorrhoea in the dancers was 20%. The lumbar spine BMD (1.006 g/cm2 vs. 0.938, P = 0.048) and hip BMD (neck of femur 0.978 g/cm2 vs. 0.838, P< 0.001; Wardʹs triangle 0.816 g/cm2 vs. 0.720, P = 0.003; trochanter 0.777 g/cm2 vs. 0.682; P< 0.001) were significantly higher in the eumenorrhoeic dancers as compared to controls. The radial BMD as measured by pQCT did not differ between the two groups, but the core trabecular tibial BMD was also higher in the dancers (321 mg/cm3 vs. 286, P = 0.006). When only oligo/amenorrhoeic dancers (n = 7) were compared with the controls, the same differences in BMD values were no longer observed. Conclusion Young women undergoing regular intensive weight-bearing exercises as in the collegiate dancers here studied have higher BMD in the axial and appendicular skeleton as compared to non-exercising females of the same age if they remain eumenorrhoeic during their training. This advantage was apparently lost when they developed oligo/amenorrhoea.