Lam IY.
Department of Obstetrics and Gynaecology, United Christian Hospital, Kwun Tong, Kowloon, Hong Kong. towkw@ha.org.hk
Study Objectives:
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 (p QCT) to determine bone density.
Settings, Design and 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/cm(2) vs. 0.938, P = 0.048) and hip BMD (neck of femur 0.978 g/cm(2) vs. 0.838, P<0.001; Ward's triangle 0.816 g/cm(2) vs. 0.720, P = 0.003; trochanter 0.777 g/cm(2) vs. 0.682; P<0.001) were significantly higher in the eumenorrhoeic dancers as compared to controls. The radial BMD as measured by p QCT did not differ between the two groups, but the core trabecular tibial BMD was also higher in the dancers (321 mg/cm(3) 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.
