Predictors And Prevalence Of Low Bone Mineral Density And Bone Stress Injuries In Ultramarathon Runners

Abstract

BACKGROUND: Low bone mineral density (BMD) and bone stress injuries (BSI) are highly prevalent among collegiate runners due to risk factors that have been well elucidated. Though initial data suggest ultramarathon runners are at high risk for low BMD and BSI, the prevalence of and risk factors for low BMD and BSI among this older population of long-distance runners has not been thoroughly investigated. PURPOSE: To determine the prevalence of and risk factors for low BMD and history of BSI in male and female ultramarathon runners METHODS: 123 ultramarathon runners who qualified for a 161km endurance race were recruited via pre-race email invitation in 2018 and 2019. Pre-race assessments included a survey on BSI history, dietary habits, body mass index and menstrual history in females; dual energy x-ray absorptiometry (DXA) scan; and, in 2019, serum evaluation for ferritin, total testosterone, free testosterone and estradiol. Poisson regression was used to evaluate risk factors for BSI; and linear regression or Pearson’s correlation coefficients when evaluating correlates of BMD. RESULTS: 40 women and 83 men (mean age 41.8 and 46.2 years, respectively) were enrolled and completed the survey with 36 women and 72 men completing DXA’s and 19 women and 32 men completing serum evaluation. 79.5% of men and 37.5% of women reported history of at least one BSI. 15% of women and 28.9% of men had low BMD (Z-score < -1.0). Low BMD was significantly or near-significantly associated with history of BSI: the age-adjusted risk ratio per BMD risk point was 1.86 (p=.036) for men and 2.03 (p=.056) for women. Oligomenorrhea was correlated with lower BMD values in women (beta coefficient=-.39 SD per risk point for total hip BMD, p=.038; and beta coefficient=-.35 SD per risk point for femoral BMD, p=.054). Of the blood markers, higher testosterone correlated with higher hip (r=.40, p=.022;) and femoral (r=.39; p=.027) BMD in males and higher estradiol correlated with higher spine BMD (r=0.47; p=.043) in females. CONCLUSIONS: BSI history and low BMD were highly prevalent among male ultramarathon runners and less so among females. Low BMD was associated with a history of BSI. Higher levels of sex hormones were correlated with higher BMD in both men and women. Oligomenorrhea was correlated with lower BMD in women.