title: Heat stress, dehydration, and kidney function in sugarcane cutters in El Salvador--A cross-shift study of workers at risk of Mesoamerican nephropathy.
abstract: BACKGROUND
  An epidemic of progressive kidney failure afflicts sugarcane workers in Central America. Repeated high-intensity work in hot environments is a possible cause.
  
  
  OBJECTIVE
  To assess heat stress, dehydration, biomarkers of renal function and their possible associations. A secondary aim was to evaluate the prevalence of pre-shift renal damage and possible causal factors.
  
  
  METHODS
  Sugarcane cutters (N=189, aged 18-49 years, 168 of them male) from three regions in El Salvador were examined before and after shift. Cross-shift changes in markers of dehydration and renal function were examined and associations with temperature, work time, region, and fluid intake were assessed. Pre-shift glomerular filtration rate was estimated (eGFR) from serum creatinine.
  
  
  RESULTS
  The mean work-time was 4 (1.4-11) hours. Mean workday temperature was 34-36 °C before noon, and 39-42 °C at noon. The mean liquid intake during work was 0.8L per hour. There were statistically significant changes across shift. The mean urine specific gravity, urine osmolality and creatinine increased, and urinary pH decreased. Serum creatinine, uric acid and urea nitrogen increased, while chloride and potassium decreased. Pre-shift serum uric acid levels were remarkably high and pre-shift eGFR was reduced (<60 mL/min) in 23 male workers (14%).
  
  
  CONCLUSIONS
  The high prevalence of reduced eGFR, and the cross-shift changes are consistent with recurrent dehydration from strenuous work in a hot and humid environment as an important causal factor. The pathophysiology may include decreased renal blood flow, high demands on tubular reabsorption, and increased levels of uric acid.
authors.affiliation: Scientific Board, Department of Investigation, Hospital Nacional Rosales, San Salvador, El Salvador. Electronic address: rgt@anhaes.org.
authors.forename: Ramón
authors.initials: R
authors.lastname: García-Trabanino
authors.affiliation: Agency for Agricultural Health and Development (AGDYSA), San Salvador, El Salvador. Electronic address: emmrijarquin@gmail.com.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Jarquín
authors.affiliation: Unit of Occupational Medicine, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden. Electronic address: inekewesseling@gmail.com.
authors.forename: Catharina
authors.initials: C
authors.lastname: Wesseling
authors.affiliation: Division of Kidney Diseases and Hypertension, University of Colorado, Denver, CO, United State. Electronic address: Richard.Johnson@ucdenver.edu.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Johnson
authors.affiliation: Research Centre on Health, Work and Environment (CISTA), National Autonomous University of Nicaragua at León, (UNAN-León), León, Nicaragua; Department of Non-communicable Disease Epidemiology of London School of Hygiene and Tropical Medicine, London, UK. Electronic address: marvin99_00@yahoo.es.
authors.forename: Marvin
authors.initials: M
authors.lastname: González-Quiroz
authors.affiliation: The La Isla Foundation, León, Nicaragua. Electronic address: ilana@laislafoundation.org.
authors.forename: Ilana
authors.initials: I
authors.lastname: Weiss
authors.affiliation: The La Isla Foundation, León, Nicaragua. Electronic address: jason@laislafoundation.org.
authors.forename: Jason
authors.initials: J
authors.lastname: Glaser
authors.affiliation: Universidad Nacional de El Salvador, El Salvador. Electronic address: juanjosevindell@gmail.com.
authors.forename: Juan
authors.initials: J
authors.lastname: José Vindell
authors.affiliation: Occupational and Environmental Medicine, Sahlgrenska University Hospital and University of Gothenburg, P.B 414, SE 405 30, Gothenburg, Sweden. Electronic address: leo.stockfelt@amm.gu.se.
authors.forename: Leo
authors.initials: L
authors.lastname: Stockfelt
authors.affiliation: Division of Kidney Diseases and Hypertension, University of Colorado, Denver, CO, United State. Electronic address: Carlos.Roncal@ucdenver.edu.
authors.forename: Carlos
authors.initials: C
authors.lastname: Roncal
authors.affiliation: Division of Kidney Diseases and Hypertension, University of Colorado, Denver, CO, United State. Electronic address: tamara.harra@ucdenver.edu.
authors.forename: Tamara
authors.initials: T
authors.lastname: Harra
authors.affiliation: Occupational and Environmental Medicine, Sahlgrenska University Hospital and University of Gothenburg, P.B 414, SE 405 30, Gothenburg, Sweden. Electronic address: lars.barregard@amm.gu.se.
authors.forename: Lars
authors.initials: L
authors.lastname: Barregard
mesh_terms: D000293:Adolescent; D000328:Adult; D003681:Dehydration / Q000150:complications* / Q000503:physiopathology; D004544:El Salvador; D000067565:Farmers; D005260:Female; D005919:Glomerular Filtration Rate; D018882:Heat Stress Disorders / Q000150:complications* / Q000503:physiopathology; D006801:Humans; D007668:Kidney / Q000503:physiopathology*; D007674:Kidney Diseases / Q000150:complications* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D031786:Saccharum; D055815:Young Adult
keywords: Chronic kidney disease; Dehydration; Heat stress; Mesoamerican nephropathy; Specific gravity; Sugarcane work; Uric acid; eGFR