Iron Deficiency in Adolescent and Young Adult German Athletes—A Retrospective Study

TL;DR

In 629 German competitive athletes, iron deficiency was common, especially in female and adolescent athletes, while manifest anemia was rare. Sport type and maximum exercise performance did not differ significantly across iron-status groups.

Key findings

• Overall iron deficiency was found in about 25% of competitive athletes and was about three times more common in women; the abstract reports 10.9% in male and 35.9% in female athletes, mainly in adolescence for males and adolescence/young adulthood for females. Manifest anemia was found in only 1.3%.
• In adult men, only one person had iron deficiency.
• There were no significant differences in iron status across sport types (skill, power, mixed, endurance) (Table 2).
• There was no significant difference in maximum workload/performance among the different iron-deficiency groups; endurance athletes had the highest performance overall (Figure 1, Tables 3 and 4).

Methods

• Retrospective analysis of 629 competitive athletes (339 male, 290 female) who presented at the Lower Saxony Olympic Training Center from May 2021–April 2022 for their annual basic sports medicine examination. Iron status was classified using Clenin criteria into normal, prelatent iron deficiency (normal Hb, low ferritin), latent iron deficiency (additionally sTFR > 4.13 mg/L or transferrin saturation < 16%), and manifest anemia; ferritin cutoffs were age-dependent (≥30 ng/mL for adults and 15–18-year-olds; ≥20 ng/mL and ≥15 ng/mL for adolescents/children). Sports were classified into skill, power, mixed, and endurance disciplines; 431 athletes performed bicycle ergometry.
• Morning blood samples were collected via antecubital vein into EDTA and lithium heparin monovettes. Ferritin values with increased C-reactive protein were excluded; sTFR and transferrin saturation were determined only when ferritin was <35 ng/mL. Anthropometric data included bioimpedance body fat; exercise testing was incremental bicycle ergometry until exhaustion with ECG and lactate monitoring.
• Statistics: mean ± standard deviation, Kolmogorov–Smirnov test, chi-squared test, ANOVA with Bonferroni-corrected post hoc tests, significance level 0.05, SPSS version 27.

Limitations

• Stated in the paper: retrospective design; extent of existing iron substitution was not recorded; no information on diet type or average daily iron intake; part of the study period fell during the peak of the COVID-19 pandemic, so not all athletes could perform the performance test; division into 32 subgroups with partly single or no athletes may have been too small to show significant differences.
• Also stated: all exercise tests used a bicycle ergometer regardless of sport type, so sport-specific testing might have revealed performance differences between iron-deficient groups; the sample was a German population with mainly Caucasian athletes, limiting generalizability to non-western or non-Caucasian populations; sport-type subdivision reflected competition load, not cardiovascular/muscular training load, and training hours per week were not classified.
• Evident from the design/text: as a retrospective observational study, it cannot establish causality between iron status and performance, and the discussion notes that a possible effect of iron substitution over time was not investigated.