Evidence Of A Cumulative Effect For Risk Factors Predicting Low Bone Mass Among Male Adolescent Athletes

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.