Heat stress symptoms & cooling center efficacy among older adults experiencing homelessness in Phoenix, Arizona

Abstract Heat relief centers (e.g. cooling or respite centers) are critical resources for protecting the public from extreme heat, particularly those experiencing unsheltered homelessness. This study evaluated older adults experiencing homelessness ( n = 44, ⩾ 55 years) who used a respite center for cooling, examining overall physiological status when entering the cooling center and during use, as well as health status, vulnerability, and adaptive capacity in relation to activity patterns and sociodemographics. Upon entering a respite center (7:00 a.m.), baseline surveys and measurements of urine specific gravity (USG), mean body temperature ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mover> <mml:mi>T</mml:mi> <mml:mo stretchy="false">¯</mml:mo> </mml:mover> </mml:mrow> <mml:mrow> <mml:mtext>b</mml:mtext> </mml:mrow> </mml:msub> </mml:mrow> </mml:mrow> </mml:math> ), skin temperature ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mover> <mml:mi>T</mml:mi> <mml:mo stretchy="false">¯</mml:mo> </mml:mover> </mml:mrow> <mml:mrow> <mml:mrow> <mml:mtext>sk</mml:mtext> </mml:mrow> </mml:mrow> </mml:msub> </mml:mrow> </mml:mrow> </mml:math> ), heart rate (HR), and blood pressure were taken. The latter three measurements occurred every 30 min for 2 h. We also examined differences between those who slept outdoors the night prior (45.5%) versus indoors (e.g. shelter). Average outdoor air temperatures for June through September were 37.4 °C (31.5 °C–43.6 °C). Participants’ average age was 61.4 years (range 55.0–70.0), with 80% male. Over half of the participants (61.3%) had at least one physical health condition, with hypertension (31.8%) and type-2 diabetes (11.4%) being the most common. The majority (56.9%) were taking medication. Participants reported a high frequency (62.5%) of thirst coinciding with underhydration (USG = 1.024 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo>±</mml:mo> <mml:mn>0.007</mml:mn> </mml:mrow> </mml:math> ). <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mover> <mml:mi>T</mml:mi> <mml:mo stretchy="false">¯</mml:mo> </mml:mover> </mml:mrow> <mml:mrow> <mml:mtext>b</mml:mtext> </mml:mrow> </mml:msub> </mml:mrow> </mml:mrow> </mml:math> and HR significantly declined with time inside. <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mover> <mml:mi>T</mml:mi> <mml:mo stretchy="false">¯</mml:mo> </mml:mover> </mml:mrow> <mml:mrow> <mml:mtext>b</mml:mtext> </mml:mrow> </mml:msub> </mml:mrow> </mml:mrow> </mml:math> dropped by 1.4 °C (baseline average of 38.4 °C [CI: 37.9–38.7 °C] to 37.0 °C [CI: 36.9–37.0 °C] after 70 min within cooling ( p &lt; 0.001). In comparing those who slept indoors versus outdoors, there were no significant differences in baseline <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mover> <mml:mi>T</mml:mi> <mml:mo stretchy="false">¯</mml:mo> </mml:mover> </mml:mrow> <mml:mrow> <mml:mtext>b</mml:mtext> </mml:mrow> </mml:msub> </mml:mrow> </mml:mrow> </mml:math> , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mover> <mml:mi>T</mml:mi> <mml:mo stretchy="false">¯</mml:mo> </mml:mover> </mml:mrow> <mml:mrow> <mml:mrow> <mml:mtext>sk</mml:mtext> </mml:mrow> </mml:mrow> </mml:msub> </mml:mrow> </mml:mrow> </mml:math> , HR, systolic and diastolic blood pressure, or USG. Findings from this population (older adults experiencing homelessness) indicate that cooling centers should ensure a minimum of 70 min for heat recovery, with extended time for rehydration. Future work should assess differing populations and exposures. Findings support cooling center operations, including capacity management, inclusion of additional services beyond cooling, and staff training.