Original Investigation
Pathogenesis and Treatment of Kidney Disease
Decreased Kidney Function Among Agricultural Workers in El Salvador

https://doi.org/10.1053/j.ajkd.2011.11.039Get rights and content

Background

An epidemic of chronic kidney disease of unknown cause has emerged along the Pacific coast of Central America, particularly in relatively young male sugarcane workers. In El Salvador, we examined residence and occupations at different altitudes as surrogate risk factors for heat stress.

Study Design

Cross-sectional population-based survey.

Setting & Participants

Populations aged 20-60 years of 5 communities in El Salvador, 256 men and 408 women (participation, 73%): 2 coastal communities with current sugarcane and past cotton production and 3 communities above 500 m with sugarcane, coffee, and service-oriented economies.

Predictor

Participant sex, age, residence, occupation, agricultural history by crop and altitude, and traditional risk factors for CKD.

Outcomes

Serum creatinine (SCr) level greater than the normal laboratory range for sex, estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m2, and proteinuria categorized as low (protein excretion ≥30-<300 mg/dL) and high grade (≥300 mg/dL).

Results

Of the men in the coastal communities, 30% had elevated SCr levels and 18% had eGFR <60 mL/min/1.73 m2 compared with 4% and 1%, respectively, in the communities above 500 m. For agricultural workers, prevalences of elevated SCr levels and eGFR <60 mL/min/1.73 m2 were highest for coastal sugarcane and cotton plantation workers, but were not increased in sugarcane workers at 500 m or subsistence farmers. Women followed a weaker but similar pattern. Proteinuria was infrequent, of low grade, and not different among communities, occupations, or sexes. The adjusted ORs of decreased kidney function for 10-year increments of coastal sugarcane or cotton plantation work were 3.1 (95% CI, 2.0-5.0) in men and 2.3 (95% CI, 1.4-3.7) in women.

Limitations

The cross-sectional nature of the study limits etiologic interpretations.

Conclusion

Agricultural work on lowland sugarcane and cotton plantations was associated with decreased kidney function in men and women, possibly related to strenuous work in hot environments with repeated volume depletion.

Section snippets

Study Design and Setting

The study was requested by the Salvadorian health authorities. Approval was obtained from the Bioethical Review Board of the Universidad Nacional in Costa Rica because there was no such entity in El Salvador at the time. All participants signed informed consent.

We selected 5 communities in El Salvador. Sugarcane production was the dominant economic activity in 2 sea-level communities on the Pacific Coast, 1 rural and 1 semirural. Previously, cotton production was important in these communities.

Study Setting and Participant Characteristics

We examined 664 persons with no exclusions (Table 1). The participation rate was 73%: 77% for women and 66% for men. The lowest response was 49% (men in the coffee community) and the highest was 86% (men in the high-altitude sugarcane community). The main reasons for refusal were no interest and anxiety about providing a blood sample. Nonresponders were of similar age as participants.

By design, there were marked differences in altitudes and economic activity between the communities and hence in

Discussion

This study provides further evidence of a CKD epidemic in Central America and data for several key characteristics. The main findings were: (1) high prevalences of elevated SCr levels and decreased eGFRs in coastal sugarcane communities with infrequent low-grade proteinuria; (2) a lower prevalence for women than men, but with similar trends over pertinent categories; (3) gradient for elevated SCr levels with years of coastal sugarcane or cotton work in men and women; and (4) no increase in

Acknowledgements

The authors acknowledge the dedication during difficult field work of assistants Gabriela Ponce, Vladimir Menjivar, Denise Membreño, David Ramírez, Jessica Ramírez, and Víctor Ramírez. We are grateful for the support from the staff at the Chemical Section of the Clinical Laboratory and nephrologists at the Nephrology Unit of Hospital Rosales and from Salvador Castillo, Dean of the Faculty of Chemistry and Pharmacy of the University of El Salvador. We thank the leaders of the different

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