Effect of brief ambient cooling on serum stress biomarkers in older adults during a daylong heat exposure: a laboratory-based heat wave simulation.

Visiting an air-conditioned location during heat exposure reduces physiological strain; however, the effects on gastrointestinal barrier dysfunction and renal ischemia remain unexplored. We compared serum protein responses during a 9 h heat exposure (40.3 °C, 9.3% relative humidity) in 17 older adults without cooling (control) and 19 older adults with a cooling break (∼23 °C) during hours 5 and 6 (cooling). IFABP and sCD14 increased similarly across groups. NGAL was 3.2 pg/mL [1.9, 6.1] lower in the cooling group during heat exposure. A 2 h cooling centre exposure did not ameliorate gastrointestinal barrier dysfunction, but did a reduce a surrogate marker of renal ischemia. ClinicalTrials.gov identifier: NCT04353076.