Heat waves and the elderly: reducing thermal and cardiovascular consequences

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Abstract Heat waves are lethal and cause a disproportionate number of deaths in the elderly relative to any other age group. It is important to note that such deaths are primarily cardiovascular, not hyperthermia itself, in origin. Nevertheless, we know relatively little about the effects of aging on cardiovascular function during actual heat wave-like conditions. The central hypothesis of this work is that the elderly exhibit greater cardiovascular stress during heat wave conditions, which can be mitigated by employing low-energy demand cooling strategies. Aim 1 will test the hypothesis that recognized impairments in thermoregulatory capacity in the elderly will culminate in heightened cardiovascular stress during prolonged exposure to heat wave conditions. Comprehensive cardiovascular and thermal responses in the elderly, relative to younger adults, will be evaluated during exposure to two prolonged heat wave conditions: hot and humid (replicating the 1995 Chicago heat wave), very hot and dry (replicating the 2018 Los Angeles heat wave). Aim 2 will test the hypothesis that skin wetting is an effective cooling modality to attenuate elevations in core body temperature and accompanying cardiovascular stress during heat waves in the elderly, while the use of a fan may be detrimental depending on air temperature and whether skin wetting is employed. Though air conditioning is the most effective strategy to prevent heat- related morbidity and mortality, 1 in 8 (~12%) Americans do not have access to air conditioners, and this percentage is likely higher in the Midwest and Northeast United States where injury and deaths during heat waves are particularly high. Moreover, factors such as socio-economic status, power outages, government- imposed rolling blackouts, and COVID-19 related closures of public spaces (e.g., malls, libraries, senior centers, etc.) threaten region-wide access to air conditioning often at times when it is most needed. Therefore, it is essential to identify non-air conditioning dependent modalities that will attenuate excessive elevations in core body temperature and associated cardiovascular stress in the elderly during heat wave conditions. This aim will assess the efficacy of skin wetting only, fan use only, and a combination of skin wetting and fan use in mitigating excessive elevations in core body temperature and associated cardiovascular stress in the elderly during both types of heat waves outlined in Aim 1. The expected outcomes from this body of work will re-shape our understanding of the consequences of aging on cardiovascular function during heat waves, as well as identify the efficacy of low-energy cooling modalities directed towards saving the lives of this vulnerable population during heat wave exposure.