The Influence Of Amenorrhea During Adolescence On Low Bone Mineral Density Of Female Runners

Female runners have a higher prevalence of low bone mineral density (BMD) and bone stress injuries. Several studies reported that amenorrhea affects low BMD in female athletes. Since adolescence is a critical period for bone mineral acquisition, amenorrhea during adolescence may be associated with low BMD in female runners. PURPOSE: To identify the relationship between amenorrhea during adolescence and low BMD in female runners. METHODS: Sixty-one female runners (aged 18-30 years) were enrolled in this cross-sectional study. The participants’ past (i.e., during their middle school and high school) and current menstrual cycles were collected, and the BMD of the whole body (WB) and lumbar spine (LS) were measured using dual-energy X-ray absorptiometry. Amenorrhea was defined as the absence of menses for at least three months or the absence of menarche at the age of 15 years or older. The prevalence of amenorrhea during middle school, high school, and at present were compared between those with and without low BMD (defined as BMD Z score ≦ -1) using chi-square tests. In addition, a linear regression analysis was performed to assess the association between the timing of the amenorrhea and low BMD. RESULTS: Of the total participants, 16 (26.2%) had low WB BMD, and 30 (49.2%) had low LS BMD. Female runners with a low WB BMD had a significantly higher prevalence of amenorrhea during middle school compared to those without low WB BMD (62.5% vs 24.4%, p = 0.006). The prevalence of amenorrhea in high school and at present were found to be similar between the two groups (42.3% vs 48.4%, p = 0.65; 37.5% vs 18.2%, p = 0.18, respectively). The linear regression analysis revealed that amenorrhea during middle school was significantly associated with low WB BMD (odds ratio, 5.152; 95% confidence interval, 1.522-17.436; p = 0.008). However, there was no significant difference in the prevalence of amenorrhea during middle school (40.0% vs 29.0%, p = 0.37), high school (46.4% vs 48.4%, p = 0.88), and at present (36.0% vs 13.0%, p = 0.098) between those with or without low LS BMD. CONCLUSION: This study identified that amenorrhea during middle school was associated with a lower WB BMD in female runners. These findings suggest that maintaining a normal menstrual cycle during periods of skeletal growth may be important in preventing low BMD in female athletes.