Heat Without Warning: Occupational Heat Stress and Cognitive Impairment Among Outdoor Workers

Hugo Moreau¹, Nikos Papadopoulos², Maria Stamataki³

Abstract

Background:
With rising global temperatures, outdoor laborers face increasing risk of heat-related illnesses. Beyond physical health, prolonged heat exposure may impair cognitive function and workplace safety, yet these effects remain poorly quantified.

Objective:
To assess the relationship between ambient heat exposure and cognitive performance among outdoor workers in urban construction and agriculture sectors.

Methods:
A prospective observational study was conducted among 244 outdoor workers in southern Italy during summer 2023. Participants underwent cognitive testing (working memory, reaction time, attention span) at baseline and after 6-hour work shifts across varying heat index categories. Continuous skin temperature, hydration status, and WBGT (Wet Bulb Globe Temperature) were monitored. Multivariable regression controlled for age, sleep, BMI, and shift duration.

Results:
Cognitive decline was observed in 63.9% of workers exposed to WBGT >30°C compared to 28.7% under moderate conditions (p < 0.001). Reaction time worsened by 17.3% on average (p = 0.004), and working memory scores dropped by 22.1% (p < 0.001). Heat exposure >6 hours was independently associated with moderate-to-severe cognitive impairment (OR: 3.6, 95% CI: 2.2–5.9). Hydration mitigated some decline, though not entirely.

Conclusion:
Chronic occupational heat stress impairs cognition and may compromise worker safety and productivity. Workplace policies should incorporate heat index forecasting, rest breaks, and hydration protocols, especially in regions facing escalating temperatures under climate change.