Background: Chronic kidney disease of non-traditional origin (CKDnt) is common among Mesoamerican sugarcane workers. Recurrent heat stress and dehydration is a leading hypothesis. Evidence indicate a key role of inflammation. Methods: Starting in sports and heat pathophysiology literature, we develop a theoretical framework of how strenuous work in heat could induce kidney inflammation. We describe the release of pro-inflammatory substances from a leaky gut and/or injured muscle, alone or in combination with tubular fructose and uric acid, aggravation by reduced renal blood flow and increased tubular metabolic demands. Then, we analyze longitudinal data from >800 sugarcane cutters followed across harvest and review the CKDnt literature to assess empirical support of the theoretical framework. Results: Inflammation (CRP elevation and fever) and hyperuricemia was tightly linked to kidney injury. Rehydrating with sugary liquids and NSAID intake increased the risk of kidney injury, whereas electrolyte solution consumption was protective. Hypokalemia and hypomagnesemia were associated with kidney injury. Discussion: Heat stress, muscle injury, reduced renal blood flow and fructose metabolism may induce kidney inflammation, the successful resolution of which may be impaired by daily repeating pro-inflammatory triggers. We outline further descriptive, experimental and intervention studies addressing the factors identified in this study.

Objectives: To examine the association between workload and kidney injury in a fieldworker cohort with different levels of physically demanding work over a sugarcane harvest, and to assess whether the existing heat prevention efforts at a leading occupational safety and health programme are sufficient to mitigate kidney injury.Methods: Biological and questionnaire data were collected before (n=545) and at the end (n=427) of harvest among field support staff (low workload), drip irrigation workers (moderate), seed cutters (high) and burned sugarcane cutters (very high). Dropouts were contacted (87%) and reported the reason for leaving work. Cross-harvest incident kidney injury (IKI) was defined as serum creatinine increase ≥0.30 mg/dL or ≥1.5 times the baseline value, or among dropouts reporting kidney injury leading to leaving work.Results: Mean cross-harvest estimated glomerular filtration rate change was significantly associated with workload, increasing from 0 mL/min/1.73 m²in the low-moderate category to −5 mL/min/1.73 m²in the high and −9 mL/min/1.73 m²in the very high workload group. A similar pattern occurred with IKI, where low-moderate workload had 2% compared with 27% in the very high workload category. A healthy worker selection effect was detected, with 32% of dropouts reporting kidney injury. Fever and C reactive protein elevation were associated with kidney injury.Conclusions: Workers considered to have the highest workload had more cross-harvest kidney damage than workers with less workload. Work practices preventing heat stress should be strengthened and their role in preventing kidney damage examined further. Future occupational studies on chronic kidney disease of unknown aetiology should account for a healthy worker effect by pursuing those lost to follow-up.

Heat stress is associated with numerous health effects that potentially harm workers, especially in a warming world. This investigation occurred in a setting where laborers are confronted with occupational heat stress from physically demanding work in high environmental temperatures. Collaboration with a major Nicaraguan sugarcane producer offered the opportunity to study interventions to prevent occupational heat-stress-related kidney disease. Two aims for this study of a rest-shade-water intervention program were: (1) describe the evolving intervention, summarize findings that motivated proposed improvements, assess impact of those improvements, and identify challenges to successful implementation and (2) extract primary lessons learned about intervention research that have both general relevance to investigations of work-related disease prevention and specific relevance to this setting. The learning curve for the various stakeholders as well as the barriers to success demonstrate that effectiveness of an intervention cannot be adequately assessed without considerations of implementation. Designing, effectively implementing, and assessing both health impacts and implementation quality is a resource-intensive endeavor requiring a transdisciplinary approach. Both general and specific lessons learned are presented for decisions on study design and study elements, implementation assessment, and management engagement in understanding how productivity and health can be successfully balanced and for building effective communication between investigators and all levels of management.

The disadvantaged populations eGFR (estimated glomerular filtration rate) epidemiology (DEGREE) study was designed to gain insight into the burden of chronic kidney disease (CKD) of undetermined cause (CKDu) using standard protocols to estimate the general-population prevalence of low eGFR internationally. Therefore, we estimated the age-standardized prevalence of eGFR under 60 ml/min per 1.73m² in adults aged 18-60, excluding participants with commonly known causes of CKD; an ACR (albumin/creatinine ratio) over 300 mg/g or equivalent, or self-reported or measured (HT) hypertension or (DM) diabetes mellitus, stratified by sex and location. We included population-representative surveys conducted around the world that were either designed to estimate CKDu burden or were re-analyses of large surveys. There were 60,964 participants from 43 areas across 14 countries, with data collected 2007- 2023. The highest prevalence was seen in rural men in Uddanam, India (14%) and Northwest Nicaragua (14%). Prevalence above 5% was generally only observed in rural men, with exceptions for rural women in Ecuador (6%) and parts of Uddanam (6%‒8%), and for urban men in Leon, Nicaragua (7%). Outside of Central America and South Asia, prevalence was below 2%. Our observations represent the first attempts to estimate the prevalence of eGFR under 60 without commonly known causes of CKD around the world, as an estimate of CKDu burden, and provide a starting point for global monitoring. It is not yet clear what drives the differences, but available evidence supports a high general-population burden of CKDu in multiple areas within Central America and South Asia, although the possibility that unidentified clusters of disease may exist elsewhere cannot be excluded.

Objective The aim of this study was to quantify the physiological workload of manual laborers in industrial sugarcane and assess the effect of receiving a rest, shade, and hydration intervention to reduce heat stress exposure risk. Methods In an observational study, physiological workload was evaluated for burned cane cutters (BCC), seed cutters (SC) and drip irrigation repair workers (DIRW) using heart rate (HR) recorded continuously (Polar®) across a work shift. Workers’ percentage of maximal HR (%HR max ), time spent in different HR zones, and estimated core temperature (ECTemp) were calculated. The effect of increasing rest across two harvests was evaluated for BCC and SC. Results A total of 162 workers participated in this study [52 BCC (all male), 71 SC (13 female) and 39 DIRW (16 female)]. Average %HRmax across a work shift was similar between BCC and SC (BCC: 58%, SC: 59%), but lower in DIRW (51%). BCC and SC spent similar proportions of work shifts at hard/very hard intensities (BCC: 13%, SC: 15%), versus DIRW who worked mostly at light (46%) or light-moderate (39%) intensities. SC maximum ECTemp reached 38.2°C, BCC 38.1°C; while DIRW only reached 37.7°C. Females performed at a higher %HR max than males across work shifts (SC 64% versus 58%; DIRW 55% versus 49%). An additional rest period was associated with a lower average %HR max across a work shift in BCC. Conclusion In this setting, BCC and SC both undertake very physiologically demanding work. Females maintained a higher workload than male co-workers. Regulated rest periods each hour, with water and shade access, appears to reduce physiological workload/strain.