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. 00:000-000, 2023. Background: Higher ferritin levels may be associated with lower cardiorespiratory fitness (CRF; i.e., maximal oxygen uptake, VO 2 max) 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, VO 2 max, 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) VO 2 max values ( r  = -0.19, p  < 0.05). In contrast, higher ferritin levels were associated with less VO 2 max 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 VO 2 max when acutely exposed to moderate altitude. The clinical relevance of these observations needs further investigation.