Effects of daylong exposure to indoor overheating on enterocyte damage and inflammatory responses in older adults: a randomized crossover trial.

We evaluated enterocyte damage (IFABP), immune activation (sCD14), and inflammatory responses (TNF-α, IL-6, CRP) in 16 older adults (66-78 years) during 8 h rest in conditions simulating homes maintained at 22 °C (control), the 26 °C indoor temperature upper limit proposed by health agencies, and homes without air-conditioning during heatwaves (31 °C, 36 °C). Relative to 22 °C, IFABP was elevated ∼181 pg/mL after exposure to 31 °C ( = 0.07), and by ∼378 pg/mL ( < 0.001) after exposure to 36 °C. No differences were observed for sCD14, TNF-α, IL-6, or CRP (all  ≥ 0.26). Our data support recommendations to maintain indoor temperatures ≤ 26 °C to preserve gastrointestinal barrier integrity in heat-vulnerable persons.