Sex differences during a cold-stress test in normobaric and hypobaric hypoxia: A randomized controlled crossover...

Area of Science:

• Human physiology
• Environmental stress response
• Sex differences in physiological adaptation

Background:

• Cold and hypoxia are common stressors, often studied together.
• Existing research on normobaric hypoxia (NH) and hypobaric hypoxia (HH) often overlooks sex-based physiological differences.
• Understanding these differences is crucial for diverse populations exposed to environmental stressors.

Purpose of the Study:

• To investigate physiological sex differences in response to a cold-stress test (CST).
• To compare responses under normoxia, normobaric hypoxia (NH), and hypobaric hypoxia (HH).
• To evaluate differences in skin temperature, cutaneous vascular conductance (CVC), oxygen saturation (SpO2), thermal sensation, comfort, and pressure pain threshold (PPT).

Main Methods:

• Ten females and ten males underwent a standardized cold-stress test (15°C for 2 minutes) on their right hand.
• The test was conducted using a randomized crossover design under three conditions: normobaric normoxia, normobaric hypoxia (NH), and hypobaric hypoxia (HH).
• Measurements included changes in skin temperature, CVC, SpO2, thermal sensation, comfort, and PPT.

Main Results:

• A significantly greater drop in hand skin temperature (∆3.3°C vs ∆1.9°C) was observed in females compared to males exclusively under normobaric hypoxia (NH) (p=0.01).
• Females reported feeling significantly colder under NH (-0.9) compared to males (-0.2) (p=0.02).
• No significant sex differences were found in CVC, SpO2, thermal comfort, or PPT across all conditions.

Conclusions:

• Females and males exhibit largely similar physiological responses to cold stress under normoxia and hypoxia.
• Specific sex differences emerge in local skin temperature regulation and thermal perception during normobaric hypoxia.
• These findings highlight the importance of considering sex as a biological variable in hypoxia and cold exposure research.