Anemia and Iron Deficiency in Strenuously Trained Adolescents.

Background: Healthy soldiers serving in combat units have a higher prevalence of anemia than age- and sex-matched civilians. This may be a “pseudo-anemia” caused by the hemodilution typical among training athletes, or a “true anemia” due to reduced total body iron stores.

Objective: To investigate the incidence of iron-deficiency anemia in recruits to the Israel Defence Forces during their first 6 months of intense combat training. This is a follow-up study to previous publication of measured values on induction.

Methods: Blood was collected from new recruits to an elite infantry unit before training. After 6 months, 153 paired samples were collected from the initial group. Total blood count and serum iron, transferrin and ferritin were measured at both time points. Soluble transferrin receptor (sTfR) was measured in 119 of the paired samples, and sTfR/log ferritin ratio was calculated.

Results: At recruitment, mean hemoglobin concentration was 14.7±0.9 g/dL (range 11.5–16.8). Iron-transferrin saturation was 34.1±13.6%, and mean ferritin concentration was 53.6±33.2 ng/mL. Twenty-seven participants (17.6%) were anemic (Hb<14g/dL), and 14.9% were iron-deficient (ferritin level <22 mg/dL). At the end of the follow-up period, 50.3% of the soldiers examined were anemic, and 27.3% had signs of iron-store depletion. Analysis of the paired samples showed an average reduction of 0.83 g/dL in hemoglobin level, and of 9.8mg/dL in ferritin levels (p<0.001 for both). sTfR increased slightly from 1.9 to 2.1mg/dL (p<0.003) among the recruits who became anemic during the follow-up period.

Conclusion: Nearly half the new recruits studied endure mild anemia after the first 6 months of training. Iron store depletion was observed among 24.5% of the cohort after 6 months, as opposed to 15% at recruitment. Overall, these changes were not accompanied by a significant increase in sTfR, but among the subset of anemic soldiers, there was a slight increase in this index. From the iron status analyses it can be concluded that in half the cases, the observed new-onset anemia was attributable to iron deficiency, and in the remainder, to hemodilution. The high incidence of iron deficiency in young healthy recruits is an important issue. The therapeutic implications of these findings require further evaluation.