Association Between Ferritin Levels and Altitude-Dependent Cardiorespiratory Fitness in Mountain Guides.

Pühringer, Reinhard, Martina Muckenthaler, and Martin Burtscher. Association between ferritin levels and altitude-dependent cardiorespiratory fitness in mountain guides. High Alt Med Biol. 24:139-143, 2023. Background: Higher ferritin levels may be associated with lower cardiorespiratory fitness (CRF; i.e., maximal oxygen uptake, VO₂max) and may represent early markers of cardiovascular risk but may also support high-altitude acclimatization. To evaluate these potential associations, data recordings from a large sample of male mountain guides have been analyzed. Methods: A total of 154 data sets (including anthropometric data, VO₂max, blood lipids, hemoglobin, ferritin, and transferrin levels) of regularly physically active and well-acclimatized mountain guides were available for analyses. Participants performed equal incremental cycle ergometer tests to exhaustion at low (600 m) and (∼1 week later) at moderate altitude (2,000 m). Results: Ferritin levels were positively correlated with levels of hemoglobin (r = 0.29, p < 0.01), total cholesterol (r = 0.18, p < 0.05), triglycerides (r = 0.23, p < 0.01), and low-density lipoprotein (r = 0.22, p < 0.01), and negatively with high-density lipoprotein levels (r = -0.16, p < 0.05) and also with baseline (taken at low altitude) VO₂max values (r = -0.19, p < 0.05). In contrast, higher ferritin levels were associated with less VO₂max decline from low-to-moderate altitude (r = 0.26, p < 0.01). Conclusion: Higher ferritin levels in male mountain guides are weakly associated with lower CRF and higher prevalence of cardiovascular risk factors but with slightly less reduction in VO₂max when acutely exposed to moderate altitude. The clinical relevance of these observations needs further investigation.