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.