Bone health in elite ballet dancers: a multidisciplinary approach

Abstract

Background It has been reported that dancers are at greater risk of developing low bone mineral density (BMD) compared to general population; however, some published studies also highlight the positive effects of dance training on bone metabolism. Given the existing controversy, the aim of the current work was a) to investigate bone health status of professional ballet dancers and vocational dance students, and b) to investigate associated factors and mechanisms involved in dancers’ bone health. Design Cross-sectional, longitudinal analysis (2-yrs follow-up) and genetic association studies were conducted on a population which consisted of professional ballet dancers, vocational dance students and controls. Methods The total of 58 professional ballet dancers (66 sex- aged-matched controls), and 152 vocational dance students (96 aged- and sex-matched controls) were screened for BMD status at impact [femoral neck (FN); lumbar spine (LS)] and non-impact sites (forearm). Tanner staging, age at menarche and menstrual status were assessed via questionnaires. Bone mass, nutrition, peak height velocity estimation, energy availability, insulin-like growth factor I (IGF-1), oestrogens, growth hormone, and sclerostin serum concentrations were longitudinally measured in a sub-sample of 101 vocational dance students and age- and sex-matched controls. Association between polymorphisms of the Wnt/β-catenin and ER signalling pathways with low BMD were further investigated. Results Female vocational dance students were more likely to display low BMD at the forearm and LS than controls (OR= 0.1; p<0.05 and OR=0.2; p<0.05, respectively); the prevalence of low BMD at the forearm was significantly higher in female professional ballet dancers than controls (37.5% vs. 17.4%, p<0.001). During the follow-up, both female and male vocational dancers revealed significantly lower BMD at impact and non-impact sites (p<0.001) compared to controls. Serum IGF-1 concentrations were significantly increased in vocational dancers compared to controls at 2yrs follow-up (p<0.05), as well as serum sclerostin (p<0.05). Genetic variants at the Wnt/β-catenin and ER signalling pathways were identified as risk factors for low BMD at both impact and non-impact sites. Conclusion Professional dancers and vocational dance students have lower bone health compared to controls. Genetic mechanisms seem to be determinant. It is recommend that dancers performing at elite level should be referred for bone densitometry.