Risk factors for stress fracture among young female cross-country runners.
OBJECTIVE
To identify risk factors for stress fracture among young female distance runners.


METHODS
Participants were 127 competitive female distance runners, aged 18-26, who provided at least some follow-up data in a randomized trial among 150 runners of the effects of oral contraceptives on bone health. After completing a baseline questionnaire and undergoing bone densitometry, they were followed an average of 1.85 yr.


RESULTS
Eighteen participants had at least one stress fracture during follow-up. Baseline characteristics associated (P<0.10) in multivariate analysis with stress fracture occurrence were one or more previous stress fractures (rate ratio [RR] [95% confidence interval]=6.42 (1.80-22.87), lower whole-body bone mineral content (RR=2.70 [1.26-5.88] per 1-SD [293.2 g] decrease), younger chronologic age (RR=1.42 [1.05-1.92] per 1-yr decrease), lower dietary calcium intake (RR=1.11 [0.98-1.25] per 100-mg decrease), and younger age at menarche (RR=1.92 [1.15-3.23] per 1-yr decrease). Although not statistically significant, a history of irregular menstrual periods was also associated with increased risk (RR=3.41 [0.69-16.91]). Training-related factors did not affect risk.


CONCLUSIONS
The results of this and other studies indicate that risk factors for stress fracture among young female runners include previous stress fractures, lower bone mass, and, although not statistically significant in this study, menstrual irregularity. More study is needed of the associations between stress fracture and age, calcium intake, and age at menarche. Given the importance of stress fractures to runners, identifying preventive measures is of high priority.
Kelsey
Jennifer L
JL
Department of Health Research and Policy, Stanford University School of Medicine, Stanford, CA, and Clinical Research Center, Helen Hayes Hospital, West Haverstraw, NY, USA. jennykelsey@comcast.net
Bachrach
Laura K
LK
Procter-Gray
Elizabeth
E
Nieves
Jeri
J
Greendale
Gail A
GA
Sowers
Maryfran
M
Brown
Byron W
BW
Matheson
Kim A
KA
Crawford
Sybil L
SL
Cobb
Kristin L
KL
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D015519:Bone Density / Q000187:drug effects*; D002136:Calcium, Dietary / Q000032:analysis; D003278:Contraceptives, Oral, Hormonal / Q000627:therapeutic use*; D005260:Female; D015775:Fractures, Stress / Q000209:etiology* / Q000517:prevention & control; D006801:Humans; D010807:Physical Endurance / Q000502:physiology; D016016:Proportional Hazards Models; D012307:Risk Factors; D012420:Running / Q000293:injuries* / Q000502:physiology; D011795:Surveys and Questionnaires; D014481:United States