Cumulative Menstrual Status is an Important Determinant of Femoral Neck Geometry in Exercising Women

Abstract

Menstrual status, both past and current, has been established as an important determinant of bone mineral density (BMD) in young exercising women. However, little is known about the association between the cumulative effect of menstrual status and bone geometry and strength. PURPOSE: To explore the association between cumulative menstrual status and estimated femoral neck (FN) geometry and strength assessed using dual-energy x-ray absorptiometry (DXA) in exercising women. METHODS: 95 exercising women (22.2±0.4 yr, BMI 21.1±0.2 kg/m2) participated in this cross-sectional study. Women were divided into three groups: 1) current and past regular menstrual cycles (C+P-R, n=23), 2) current and past irregular menstrual cycles (C+P-IR, n=51), and 3) current or past irregular cycles (C/P-RIR, n=21). Estimates of FN geometry and strength were obtained from hip strength analysis. Cross-sectional moment of inertia (CSMI), cross-sectional area (CSA), and strength index (SI) were calculated at the FN. Low CSMI, CSA, and SI were operationally defined as values below the median. Chi-square tests and multivariable logistic regression were performed to compare the prevalence and determine the odds, respectively, of low CSMI, CSA, and SI among groups. RESULTS: The groups did not differ in weight, height, BMI, or body composition (p>0.05); however, the C+P-IR group was younger than the C+P-R group (p=0.023). Cumulative menstrual status was a significant predictor of low FN CSMI and low FN CSA after controlling for confounding variables. When compared with the C+P-R group, the odds of C+P-IR women having low FN CSMI were 7.3 times greater (95% CI: 1.6-34.0, p=0.011) and the odds of C/P-RIR women having low FN CSA were 4.5 times greater (95% CI: 1.1-18.9, p=0.039). Chi square analysis revealed no significant association between menstrual group and low FN CSMI, CSA, or SI (p>0.05). CONCLUSION: In exercising women, the cumulative effect of current and past menstrual irregularity appears to be an important predictor of smaller estimates of FN geometry, which may serve as another means, beyond BMD, by which menstrual irregularity compromises bone strength. These findings support the recommendation that current and past menstrual status should be evaluated in female athletes when assessing bone health. Supported by US DoD (PR054531)