Cardiovascular and Thermal Responses to Cold Exposure During Exercise in Iron-Deficient Anemic Individuals

Background: Temperature regulation is impaired in iron-deficient anemic humans and rats at rest during cold exposure. However, there is a paucity of data regarding the interplay of cold exposure, anemia, and exercise on thermal and cardiovascular responses. Therefore, we aimed to explore thermal and cardiovascular responses of individuals with chronic mild iron-deficiency anemia during exercise in the cold compared to controls. Methods: Nine anemic (5 F, 4 M) and nine control (5 F, 4 M) individuals, matched for body fat, size, and mass but different by design in hematological parameters and physical fitness, participated in the study. The participants cycled in cold 11 °C with 40% relative humidity (RH) and neutral (22 °C, 40% RH) conditions at an intensity ~10% below the respiratory threshold until 1 °C increase in rectal temperature (T_re) or 1 h of exercise, whichever occurred first. Results: In the cold, the anemic individuals showed a lower rate of T_re rise (p = 0.047) and lower mean skin temperature (T_sk) (p = 0.03) compared to controls, while only controls increased heat production compared to the neutral condition (p = 0.035). Moreover, the anemic group exhibited an exaggerated blood pressure response in the cold compared to the neutral environment (p < 0.05), due to heightened total peripheral resistance (p < 0.05) and vasomotor response (p < 0.001). Conclusions: In summary, chronic mild iron-deficiency anemia impaired temperature regulation as judged from the lower rate of T_re rise and an inability to activate further the metabolism at cold. Concomitantly, the anemic participants demonstrated increased cardiovascular strain. This is notable because anemia and these environmental conditions are encountered in the workplace, recreational activities, and athletic endeavors. These findings may inform safety guidelines for athletes, workers, and patients exposed to cold environments.