The Association between Hematological and Inflammatory Factors and Stress Fractures among Female Military Recruits

Abstract

With the growing number of females accepted for combat-related military duties in the Israeli Defense Forces, their special needs should be addressed. Previous studies on females in combat training have found a high prevalence of iron deficiency at recruitment as well as an increased rate of stress fractures (SF) and overuse injuries during training when compared with males. The aim of this study was to assess the correlation between hematological and inflammatory variables and SF occurrence among military recruits during basic training. Three gender-integrated light infantry units were followed prospectively. Female recruits inducted for medic and dental assistants' courses were followed for comparison. Hemoglobin, iron, transferrin, ferritin, C-reactive protein, and interleukin-6 levels were measured for all participants at recruitment and at 2 and 4 months of training. SF were diagnosed radiographically or scintigraphically according to the Israeli Defense Forces protocol. A total of 438 subjects were recruited (female combatants = 227, male combatants = 83, noncombatant females = 128). At induction, 18% of female combatants had anemia compared with 8% of males and 19% of noncombatants. Iron deficiency was noted in 40%, 6%, and 38%, respectively. There were no clinically significant changes during training. Twelve percent of female combatants developed SF, whereas none occurred among male combatants or noncombatants. Subjects sustaining an SF had significantly lower levels of serum iron and iron saturation. A high incidence of anemia as well as iron deficiency was found in this young asymptomatic cohort, with no significant change during training. The lower level of iron in female combatants sustaining SF warrants further investigation.