Sex-specific considerations in thermal physiology

Males and females differ somewhat in their responses to heat stress, largely due to females having a reduced sweating capacity, specifically during periods of high heat loss requirements. Furthermore, hormonal fluctuations associated with the menstrual cycle modify responses to heat strain. For example, elevated progesterone concentrations during the luteal phase of the menstrual cycle increases resting body temperature, the onset threshold for sweating, and cutaneous vasodilation for heat dissipation. Furthermore, perimenopausal and menopausal females experience additional heat sensitives, with the occurrence of hot flushes and night sweats which elevate their thermal discomfort. Interestingly, females report feeling less prepared for a heat wave than males, experience more heat illness symptoms during a heat wave (Mee et al., manuscript in preparation), are more commonly diagnosed with heat illnesses, and there are more excess deaths reported in females during heat waves.
Despite compelling evidence of sex differences in responses to heat strain, detailed audits of research designed to reduce physiological strain and susceptibility to exertional heat illness reveal a substantial under-representation of females as study participants. Of that data that is available, females have been shown to differ in their heat adaptive responses, with females typically requiring additional thermal stimuli to achieve the same magnitude of adaptation compared to males. Furthermore, most studies evaluating acute heat mitigation strategies in female participants, have failed to establish a reduction in physiological strain, thus, the efficacy of acute heat mitigation strategies in females is limited. The lack of robust thermal research on female-specific considerations ultimately hinders consensus on female bespoke guidance. For example, heat mitigation guidelines, which aim to reduce physiological strain and susceptibility to exertional heat illness, are underpinned almost exclusively by research conducted in males, without consideration of issues associated with the biological and phenotypical sex differences, despite females likely being at greater risk.
Heat illnesses are largely avoidable with the implementation of appropriate, effective, accessible, and sustainable heat mitigation strategies combined with appropriate education. Very few individuals receive any heat mitigation guidance from their employer or access public guidance on how to stay safe during heat waves (Mee et al., manuscript in preparation). Despite this lack of education, females have reported a greater willingness (compared to males) to engage with educational resources to enable them to optimise their preparation for a heat wave and reduce the impact the extreme heat has on their health and wellbeing (Mee et al., manuscript in preparation). As such, furthering our understanding of how females respond to heat strain and heat mitigation strategies whilst enhancing the translation of research informed strategies to the lay public is of urgent priority.