The relation between stress fractures and bone mineral density: Evidence from active-duty army women

ObJective: To determine if bone mineral density (BMD) is associated with the probability of stress fractures in premenopausal women. Design: Case- control study. Setting: Large Army post, Fort Lewis, WA. Participants: Twenty-seven active duty Army women with documented stress fractures within the last 2 years and 158 female controls. Methods and Main Results: All subjects were examined and interviewed. BMD of the femoral neck and posteroanterior lumbar spine (L2-L4) was measured using dual energy X-ray absorptiometry. Univariate comparisons revealed no significant differences in BMD of the femoral neck or lumbar spine between groups. Women with stress fractures had a significantly higher exercise intensity (428 vs 292 minutes per week, p < .05) and were more likely to be entry-level enlisted soldiers (63% vs 44%, p < .05) than those without stress fractures. Multivariate analyses revealed a strong negative association between femoral neck BMD and the probability of stress fractures (lower BMD, higher risk). Exercise intensity and body mass index had a significant positive effect on BMD of the femoral neck and lumbar spine, yet both were associated with an increased probability of stress fractures. Conclusions: Femoral neck BMD was significantly associated with the probability of stress fractures. Optimal training programs should balance the beneficial indirect effect of increased exercise (through increased BMD) with its detrimental direct effect on stress fractures.