Prospective cohort study of the risk factors for stress fractures in Chinese male infantry recruits

Objective To determine potential risk factors that could predict stress fractures over an 8-week basic military training in Chinese male infantry recruits. Methods Recruits from three infantry units enrolled in this prospective study. At baseline, demographic data, personal history of stress fractures, mean duration of weekly exercise and smoking history were recorded on questionnaires and blood samples taken for analysis of bone turnover biomarkers and genetic factors. Results Of the 1516 male recruits who volunteered to participate in the study, 1398 recruits provided data for analysis. In total, 189 stress fracture cases were observed (incidence rate: 13.5%) during the 8-week training period. Recruits with stress fractures had a significantly higher incidence of prior fracture history and lower exercise level prior to enrolment compared with those without stress fractures. A significant difference in both allelic frequency and genotypic distribution of the growth differentiation factor 5 (GDF5) gene rs143383 polymorphism was observed between recruits with and without stress fractures. However, no difference in serum bone turnover biomarkers was detected between groups. Conclusion This prospective, cohort study indicates that fracture history, lower exercise level and GDF5 rs143383 may be predictive risk factors for stress fractures in Chinese male infantry recruits.