Prevalence and Risk Factors for CKD Among Brickmaking Workers in La Paz Centro, Nicaragua.

RATIONALE & OBJECTIVE: In Central America, there is a high prevalence of chronic kidney disease (CKD) of nontraditional etiology often observed among agricultural workers. Few studies have assessed CKD prevalence among workers in nonagricultural occupations, which was the objective of this investigation. STUDY DESIGN: Prospective cohort study. SETTING & PARTICIPANTS: Male and female workers (n = 224) employed by artisanal brickmaking facilities in La Paz Centro, Nicaragua. PREDICTORS: Age, sex, education, smoking status, body mass index, alcohol consumption, water consumption, first-degree relative(s) with CKD, years worked, hours worked per week, job category, study visit (baseline and follow-up), and self-reported hypertension and diabetes. OUTCOMES: CKD defined as estimated glomerular filtration rate (eGFR) < 60mL/min/1.73m2 at 2 time points 4 months apart and CKD stage. ANALYTICAL APPROACH: A linear mixed-effects model with an unstructured covariance matrix was used to evaluate the association between demographics, occupational risk factors, and eGFR at baseline. The interaction between risk factors and time with change in eGFR was also evaluated. Multivariable logistic regression models were used to evaluate predictors of CKD. RESULTS: The CKD prevalence was 12.1% (n = 27), 100% of cases were male, 30% had stage 5 CKD (eGFR < 15mL/min/1.73m2), and 22% were younger than 35 years. Proportions of participants with eGFRs < 60mL/min/1.73m2 at baseline and follow-up were 13.8% and 15.2%, respectively. Linear regression analysis demonstrated significant predictors of lower kidney function at baseline including oven work, older age, lack of education, and having an immediate family member with CKD. Predictors of CKD identified using logistic regression analysis included oven work and lack of education. LIMITATIONS: Crude job classification measures, loss to follow-up, self-reported exposures. CONCLUSIONS: The prevalence of CKD is high in this population of brick workers, suggesting that the epidemic of CKD affecting Mesoamerica is not limited to agricultural workers. These results are consistent with the hypothesis that occupational heat exposure is a risk factor for kidney disease in this region.

Acute Kidney Injury in Sugarcane Workers at Risk for Mesoamerican Nephropathy.

RATIONALE & OBJECTIVE: Mesoamerican nephropathy (MeN), a form of chronic kidney disease (CKD) of unknown cause in Central America, affects young individuals working in physically strenuous occupations. Repeated episodes of work-related kidney injury may lead to CKD in this setting. We aimed to better understand the burden and natural history of acute kidney injury (AKI) in workers at risk for MeN. STUDY DESIGN: Cross-sectional study of active sugarcane workers, followed by prospective follow-up of individuals with AKI. SETTING & PARTICIPANTS: 326 sugarcane workers with normal preharvest serum creatinine (Scr) values and no history of CKD in an MeN hotspot in Nicaragua near the end of the harvest, and prospective follow-up of workers with AKI. PREDICTOR: AKI during the harvest, as defined by Scr level increase ≥ 0.3mg/dL over baseline to a level ≥ 1.3mg/dL. OUTCOMES: Kidney function trajectory and development of CKD over 12 months. ANALYTICAL APPROACH: Linear regression models were used to analyze the association between job category and kidney function. For workers with AKI, the effect of time on Scr level was evaluated using linear mixed effects. RESULTS: 34 of 326 participants were found to have AKI, with a median late-harvest Scr level of 1.64mg/dL in the AKI group. Workers without AKI had a median Scr level of 0.88mg/dL. AKI was more common among cane cutters compared with other field workers. Participants with AKI had variable degrees of kidney function recovery, with median 6- and 12-month Scr values of 1.25 and 1.27mg/dL, respectively (P < 0.001 for each follow-up value compared to late-harvest Scr). When we compared workers' kidney function before the AKI episode to their kidney function at last follow-up, 10 participants with AKI developed de novo estimated glomerular filtration rate < 60mL/min/1.73m2 and 11 had a >30% decrease in estimated glomerular filtration rate. LIMITATIONS: Follow-up limited to 1 year and some loss to follow-up in the prospective component of the study. Broad definition of AKI that includes both acute and subacute kidney injury. CONCLUSIONS: In a group of sugarcane workers with normal preharvest kidney function, newly decreased kidney function developing during the harvest season was common. Of those with kidney injury, nearly half had established CKD 12 months later.

Urinary Metals Concentrations and Biomarkers of Autoimmunity among Navajo and Nicaraguan Men.

Metals are suspected contributors of autoimmune disease among indigenous Americans. However, the association between metals exposure and biomarkers of autoimmunity is under-studied. In Nicaragua, environmental exposure to metals is also largely unexamined with regard to autoimmunity. We analyzed pooled and stratified exposure and outcome data from Navajo (n = 68) and Nicaraguan (n = 47) men of similar age and health status in order to characterize urinary concentrations of metals, compare concentrations with the US National Health and Nutrition Examination Survey (NHANES) male population, and examine the associations with biomarkers of autoimmunity. Urine samples were analyzed for metals via inductively coupled plasma mass spectrometry (ICP-MS) at the US Centers for Disease Control and Prevention. Serum samples were examined for antinuclear antibodies (ANA) at 1:160 and 1:40 dilutions, using an indirect immunofluorescence assay and for specific autoantibodies using enzyme-linked immunosorbent assay (ELISA). Logistic regression analyses evaluated associations of urinary metals with autoimmune biomarkers, adjusted for group (Navajo or Nicaraguan), age, and seafood consumption. The Nicaraguan men had higher urinary metal concentrations compared with both NHANES and the Navajo for most metals; however, tin was highest among the Navajo, and uranium was much higher in both populations compared with NHANES. Upper tertile associations with ANA positivity at the 1:160 dilution were observed for barium, cesium, lead, strontium and tungsten.

Environmental and Occupational Exposures in Kidney Disease.

More than 8 million deaths each year are attributed to noncommunicable environmental hazards where people live, work, and play. Physical or chemical hazards may be inhaled, ingested, or absorbed through the skin, affecting all organ systems, including the kidney. Heavy metals, pesticides, and infections are some of the environmental hazards associated with kidney dysfunction and chronic kidney disease. The severity of the effects of these exposures likely is modulated by the timing and duration of exposure, genetic susceptibility, and other conditions, and may lead to the development of acute and/or chronic kidney disease. In this review, we discuss environmental exposures that are associated with kidney dysfunction in animals and human beings, with a focus on those implicated in causing chronic kidney disease.