Climate change is intensifying occupational heat exposure, posing risks not only for heat-related illness but also for sleep, which is essential for recovery, safety, and productivity. Heat-exposed workers are highly vulnerable due to prolonged exposure, limited access to cooling, and poor housing. This systematic review aimed to synthesise global evidence on how occupational heat exposure affects sleep quality among workers across different occupations and settings. A systematic review was conducted following Synthesis without Meta-Analysis (SWiM) guidelines. PubMed, Scopus, and Google Scholar were searched (2000–2025) for studies involving adult workers (≥18 years) reporting both heat exposure and sleep outcomes. The review was registered with PROSPERO (ID: CRD420251125735). Of 7,108 records screened, 11 studies met the inclusion criteria. Studies spanned Asia, Australia, North America, and global cohorts. Heat exposure consistently impaired sleep quality and duration. Using Pittsburgh Sleep Quality Index, Actigraphy, and self-reports, common complaints included difficulty falling asleep (64%), restlessness (54%), non-restorative sleep (54%), night sweats (36%), and reduced total sleep time (45%). Night-time temperatures above 25°C and high workplace wet bulb globe temperature values were strongly linked with reduced sleep efficiency and delayed sleep onset. Vulnerable groups included shift workers, petrochemical and steel labourers, women, older adults, and low-income workers in urban heat islands and poorly ventilated housing. Occupational heat exposure disrupts sleep, compounding daytime strain and creating a dual burden for workers. Integrating sleep into heat stress management through cooling interventions, better housing, and revised work–rest schedules is critical for workers well-being in a warming climate.

BACKGROUND: Workers laboring in steel industries in tropical settings with high ambient temperatures are subjected to thermally stressful environments that can create well-known risks of heat-related illnesses and limit workers’ productivity. METHODS: A cross-sectional study undertaken in a steel industry in a city nicknamed “Steel City” in Southern India assessed thermal stress by wet bulb globe temperature (WBGT) and level of dehydration from urine color and urine specific gravity. A structured questionnaire captured self-reported heat-related health symptoms of workers. RESULTS: Some 90% WBGT measurements were higher than recommended threshold limit values (27.2–41.7°C) for heavy and moderate workloads and radiational heat from processes were very high in blooming-mill/coke-oven (67.6°C globe temperature). Widespread heat-related health concerns were prevalent among workers, including excessive sweating, fatigue, and tiredness reported by 50% workers. Productivity loss was significantly reported high in workers with direct heat exposures compared to those with indirect heat exposures (χ2 = 26.1258, degrees of freedom = 1, p < 0.001). Change in urine color was 7.4 times higher among workers exposed to WBGTs above threshold limit values (TLVs). CONCLUSION: Preliminary evidence shows that high heat exposures and heavy workload adversely affect the workers’ health and reduce their work capacities. Health and productivity risks in developing tropical country work settings can be further aggravated by the predicted temperature rise due to climate change, without appropriate interventions. Apart from industries enhancing welfare facilities and designing control interventions, further physiological studies with a seasonal approach and interventional studies are needed to strengthen evidence for developing comprehensive policies to protect workers employed in high heat industries.
Climate Change ; Cross-Sectional Studies ; Dehydration ; Efficiency* ; Fatigue ; Hot Temperature* ; India* ; Seasons ; Specific Gravity ; Steel* ; Sweat ; Sweating ; Threshold Limit Values