Background Limited research has evaluated risk factors for low bone mineral density (BMD) in male adolescent athletes.
Aims/objectives To evaluate predictors of low BMD (defined as BMD Z-score <−1.0) in a sample of male adolescent distance runner and non-runner athletes.
Methods Male adolescent athletes completed a survey characterising sports participation, nutrition, stress fracture history, dual energy X-ray absorptiometry (DXA)-measured BMD and body composition. Independent t-tests and analysis of covariance (ANCOVA) evaluated group differences; logistic regression evaluated low BMD risk factors.
Results Runners (n=51) exhibited a lower body weight (p=0.02), body mass index (BMI) (kg/m2) (p=0.02), per cent expected weight (p=0.02) and spine BMD Z-score (p=0.002) compared with non-runners (n=18). Single risk factors of low BMD included <85% expected weight (OR=5.6, 95% CI 1.4 to 22.5) and average weekly mileage >30 in the past year (OR=6.4, 95% CI 1.5 to 27.1). The strongest two-variable and three-variable risk factors included weekly mileage >30+ stress fracture history (OR=17.3, 95% CI 1.6 to 185.6) and weekly mileage >30+<85% expected weight + stress fracture history (OR=17.3, 95% CI 1.6 to 185.6), respectively. Risk factors were cumulative when predicting low BMD (including <85% expected weight, weekly mileage >30, stress fracture history and <1 serving of calcium-rich food/day): 0–1 risk factors (11.1%), 2 risk factors (42.9%), or 3–4 risk factors (80.0%), p<0.001).
Conclusions Male adolescent runners exhibited lower body weight, BMI and spine BMD Z-score values. The risk of low BMD displayed a graded relationship with increasing risk factors, highlighting the importance of using methods to optimise bone mass in this population.
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Contributors MTB led the manuscript writing, data analysis, participated in study design and project coordinating at the UCLA site. MF served as PI at the Stanford site, AN served as PI at the UCLA site, AT was project coordinator at the Stanford site. AN, MF and AT participated in writing, reviewing and editing the manuscript.
Funding The study received financial support from the UCLA Clinical and Translational Science Institute (grant #UL1TR000124) and the 2010 Richard S Materson Education Research Fund New Investigator Research Grant, Stanford Medical Scholars Research Program, Education Research Fund for Physical Medicine and Rehabilitation Medical Student Research Grant (awarded to AST).
Competing interests None declared.
Ethics approval UCLA IRB, Stanford University IRB.
Provenance and peer review Not commissioned; externally peer reviewed.
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