Low bone mineral density is two to three times more prevalent in non-athletic premenopausal women than in elite athletes: a comprehensive controlled study.

Objective: To compare bone mineral density (BMD), investigate factors associated with BMD, and examine the prevalence of low BMD in athletes and non-athletic controls.

Methods: The study included a questionnaire (part I), measurement of BMD (part II), and a clinical interview (part III). All Norwegian female athletes on national teams (n = 938) and an aged matched random sample of non-athletic controls (n = 900) were invited to participate. The questionnaire was completed by 88% of athletes and 70% of controls. A random sample of these athletes (n = 300) and controls (n = 300) was invited to participate in parts II and III. All parts were completed by 186 athletes (62%) and 145 controls (48%).

Results: Mean (standard deviation) total body (TB) BMD was higher (p<0.001) in athletes (1.21 (0.09) g/cm2) than in controls (1.18 (0.08) g/cm2), and higher (p<0.001) in high impact (HI) sports athletes than in medium impact (MI) and low impact (LI) sports athletes. In athletes, body weight and impact loading sports were positively associated, and percent body fat and eating disorders were negatively associated with TB BMD. Body weight and weight bearing activities were positively associated and menstrual dysfunction was negatively associated with TB BMD in controls. A higher percentage of controls (28.3%) than athletes (10.7%) had low BMD (p<0.001).

Conclusion: Female elite athletes have 3-20% higher BMD than non-athletic controls and HI sports athletes have 3-22% higher BMD compared with MI and LI sports athletes. Low BMD is two to three times more common in non-athletic premenopausal women than in elite athletes.