Occupational heat exposure and kidney disease - Studies on the role of heat stress in the Mesoamerican epidemic of Chronic Kidney Disease of non-traditional origin

Abstract

This thesis examines the association between heat stress and kidney disease in Mesoamerica using different perspectives and methods. An ecologic study found that hot, sugarcane-cultivating regions had elevated chronic kidney disease (CKD) mortality. In a longitudinal workplace study, kidney injury incidence was higher among sugarcane harvest workers with high physical workload, and decreased with an intervention reducing heat stress. Low liquid intake and consumption of NSAIDs were additional risk factors for kidney injury. Kidney injury coincided with fever and elevated levels of inflammation biomarkers, suggesting that inflammation mediated kidney injury. These findings are consistent with excessive heat strain from high internal heat production and external heat load being a main cause of the Mesoamerican epidemic of CKD of non-traditional origin (CKDnT). Kidney injury assessed by repeat serum creatinine (SCr) measurements corresponded well to increasing levels of urine kidney injury markers and decreasing serum erythropoietin, strengthening SCr increase as an intermediary outcome. The implications of the findings for future research, and public and occupational health practice in low-income settings facing global warming are discussed.