Heat-related illness symptoms among migrant farmworkers: a systematic literature review and meta-analysis

BACKGROUND: Farmworkers are at risk for heat-related illnesses (HRI) due to intensifying heat exposure resulting from climate change. Migrant farmworkers might be at further increased risk due to limited control over workplace conditions and language and cultural barriers. This systematic literature review and meta-analysis aims to assess the global prevalence of self-reported heat-related illnesses among migrant farmworkers. METHODS: We searched five databases for peer-reviewed literature and additional sources to capture grey literature in any language up to October 2024. Studies providing self-reported heat-related symptoms among migrant farmworkers were included. A random effects model was used to calculate the pooled proportion of individual and combined heat-related health outcomes. Separate pooled estimates were included for each symptom as well as the number of symptoms. Risk of bias was assessed using the JBI quality assessment tool. RESULTS: Seventeen papers were included, including data from 2966 migrant farmworkers. The pooled proportion for having at least one HRI symptom was 52% (95%CI 39-65) and 21% (95%CI 4-44) reported at least three HRI symptoms. Heterogeneity was high across all pooled estimates (I² ranging from 83% to 99%). The most common symptoms were extreme sweating (46%), weakness (45%), and headache (36%). No differences were found between internal and international migrants nor between studies asking about HRI symptoms experienced in a short-term (e.g., the past week) versus longer periods. DISCUSSION AND CONCLUSION: Migrant farmworkers reported a high proportion of HRI symptoms. Standardized HRI symptom questionnaires and physiological monitoring can aid in early detection to prevent more serious health issues, allow comparison across settings, and support interventions to mitigate heat-related occupational health risks.