Rising temperatures and increasing extreme heat events pose severe health risks to informal workers, particularly those engaged in labor-intensive occupations. This pilot study investigates the comparative prevalence of heat-related symptoms among indoor and outdoor informal workers in Dhaka, Bangladesh, identifies key sociodemographic and occupational risk factors, and examines the association between heat stress and heat stroke.

A cross-sectional study was conducted among 416 informal workers using structured interviews. Temperature data were obtained from the Bangladesh Meteorological Department and satellite imagery. Heat-related symptoms were assessed using a validated questionnaire, and statistical analyses included independent t -tests, one-way ANOVA, and binary logistic regression to identify significant predictors of symptom severity and heat stroke risk.

Weakness/tiredness (82.45 %), heavy sweating (94.47 %), and headaches (68.75 %) were the most commonly reported symptoms. Outdoor workers exhibited significantly higher symptom scores than indoor workers ( p < 0.05), particularly for muscle cramps, weakness, and headaches, reflecting their greater exposure to extreme heat. Age ( p = 0.544), education level ( p = 0.003), and occupation ( p = 0.034) were significantly associated with symptom severity. Older individuals, workers with no formal education, and those in physically demanding or exposed occupations such as day laborers, construction workers, and rickshaw pullers reported the highest symptom scores. A strong association between heat-related symptoms and heat stroke was found, particularly among outdoor workers (Exp(B) = 1.236, p < 0.001).

This pilot study underscores the urgent need for targeted heat adaptation strategies, including workplace cooling measures, rest breaks, and hydration access, to mitigate occupational health risks among informal workers in rapidly urbanizing regions.