Cognitive Performance in Young Adults During Three Consecutive Days of Simulated Occupational Heat Stress: An...

Global increases in occupational heat exposure are raising concerns about worker safety and cognitive performance during prolonged and repeated shifts. At present, the cumulative effects of repeated heat exposure on cognitive performance remain unclear. This exploratory study examined cognitive performance and perceived workload across three consecutive days of simulated occupational heat stress.

Twenty physically active adults (age: 27 ± 6 years [5 female]) completed two randomized crossover trials comprising three consecutive 8-h workdays under hot (35°C; 63% RH; WBGT 31°C) and control (18°C; 53% RH; WBGT 14°C) conditions wearing minimal clothing (< 1 Clo). Participants performed moderate-intensity physical work (~4.3 METs) using a 30-min work:30-min rest schedule. Cognitive performance was assessed at start-of-day, midday, and end-of-day using the Joggle Research battery, evaluating sensorimotor speed, processing speed, and attention, visuospatial perception, sustained attention, and visual memory. Perceived workload was assessed at start-of-day and end-of-day using the NASA Task Load Index.

Cognitive performance was largely preserved across domains within and across repeated workdays, with no evidence of cumulative impairment (p ≥ 0.170). Unexpectedly, sustained attention improved in the heat. Perceived physical workload was higher in the heat, while perceived mental workload was unchanged.

Under prescribed work-rest conditions, cognitive performance appears to be maintained across consecutive days of occupational heat exposure in young, physically active adults. Future work should explore the relationship between heat and cognition in larger, more diverse work populations and in more challenging conditions.