Author(s): JONVIK, K., ØISTUEN, G.F., OSBORNE, J.O., SUNDGOT-BORGEN, J., NOORDHOF, D.A., TAYLOR, M.Y., HEIKURA, I., STELLINGWERFF, T., SOLHEIM, S.A., LUNDBERG, H.E., MATHISEN, T.F., HANSEN, M., OZFELDT, M., DALGAARD, L.B., ANDERSSON, E.P., MADSEN, K., Institution: NORWEGIAN SCHOOL OF SPORT SCIENCES, Country: NORWAY, Abstract-ID: 986

INTRODUCTION:
Relative energy deficiency in sport (REDs) is a syndrome caused by problematic low energy availability, where known symptoms are menstrual disturbances (MD) and low bone mineral density (BMD, Z-score <-1.0). The magnitude of these issues and their relationships across different sports requires further attention. This study aimed to 1) investigate the rate of severe MD and low BMD between athletes from different sports, 2) compare BMD Z-scores at lumbar spine, hip and whole-body between women with regular menstruation (RM), severe MD and those using hormonal contraceptives (HC), and 3) investigate which factors are related to BMD among endurance athletes such as menstrual status, athletic caliber and sport-specific loading characteristics.
METHODS:
Cross-sectional data from seven different projects in Norway, Denmark and Canada included 411 women representing 34 different sports (grouped as endurance: n=257 and non-endurance: n=154) and a wide range in athletic caliber (Tier 0 (sedentary) to 5 (world-class)). BMD was measured using Dual X-ray absorptiometry. Menstrual status was defined by the three-step method or questionnaires, and participants were grouped based on menstrual status (RM, severe MD, and HC). The endurance sports were also categorized by sport-specific loading characteristics (very low, low and medium).
RESULTS:
Among non-HC users (51%), the rate of severe MD was similar in endurance (37%) and non-endurance athletes (35%). No significant association of menstrual status was observed for lumbar spine (P=0.334), hip (P=0.079) or whole-body BMD (P=0.164). Endurance athletes had lower BMD Z-score at lumbar spine compared to non-endurance athletes (-0.0±1.0 vs 1.2±1.2, P<0.0001), with a higher rate of low BMD (17% vs 2%, P=0.015). At the hip, BMD Z-score was lower in endurance compared to non-endurance athletes (0.6±0.9 vs 1.4±1.2, P<0.05 for age<27), with no differences at the whole-body level. Among endurance athletes, neither sport-specific impact characteristics nor athletic caliber showed a significant association with BMD at any site (all P>0.05). However, endurance athletes with severe MD had lower hip BMD Z-scores compared to RM athletes (P=0.008) and HC users (P=0.021), while menstrual status showed no significant association with lumbar spine and whole-body BMD.
CONCLUSION:
The rate of severe MD did not differ between endurance and non-endurance athletes. BMD Z-scores did not differ across menstrual status categories. However, endurance athletes had lower BMD Z-scores compared to non-endurance athletes, with hip BMD being even lower in endurance athletes with severe MD. Future research should focus on combining a full REDs assessment with detailed data on training history, bone loading impact and injuries in female athletes from different sports.