Abstract
Rising heat waves and elevated indoor temperatures raise concerns about the resilience of cognitive functions to minor shifts in microclimate, which is significant because individuals spend up to 90% of their time indoors. Previous research indicates that moderate warming and increased CO₂ levels can impair reaction speed, accuracy, and executive control, although the effects vary depending on temperature ranges and methodologies. However, the combined impact of heat, CO₂, and humidity within the typical 22–30 °C range remains insufficiently characterized. This study addresses the broader issue of how moderate heat stress and concurrent changes in air quality influence specific cognitive domains in healthy young adults. In a pilot crossover study, 10 participants completed two sessions: a thermoneutral condition (23–24.8 °C) and an elevated heat-stress condition (>27 to approximately 30 °C) with continuous monitoring of temperature, humidity, CO₂, particulate matter, noise, and eTVOC. Cognitive performance was assessed using standardized CogniFit tests. The findings demonstrate that higher temperatures are associated with increases in group scores for reasoning, coordination, perception, and memory, whereas attention appears most vulnerable, showing mixed or decreased responses. Domain-specific correlations were identified: humidity significantly degrades perception (r = −0.66), temperature moderately supports coordination (r = 0.34), and attention exhibits a negative association with temperature (r = −0.19). These results refine the common assumption of a uniform decline under moderate warming, revealing that effects are heterogeneous and domain-dependent, with attention being the most sensitive indicator. In a broader context, the findings support adaptive microclimate management targeting temperature and humidity according to current cognitive tasks and demonstrate the applicability of an IoT-integrated platform (e.g., Home Assistant with automated ventilation at CO₂ > 1000 ppm) for research and practical applications. Ultimately, this pilot study lays the groundwork for deploying real-world systems with online analytics and adaptive algorithms.