Objectives Chronic kidney disease (CKD) unrelated to conventional risk factors occurs in Central America, mostly in younger, male agricultural workers. We explored residence and occupation at different altitudes in El Salvador as surrogates for heat stress.

Methods In a population-based survey we determined prevalences of elevated serum creatinine (S-Cr) (≥1,2 and 0.9 mg/dl in males and females), CKD ≥ stage 3 (glomerular filtration rate <60 ml/min/1.73 m2) and proteinuria among occupational subgroups of the populations age 20–60 of five Salvadorian communities, together 256 men and 408 women (participation 73%). Logistic regressions assessed associations between kidney function and agricultural occupations by altitude and sex, adjusting for conventional risk factors.

Results Among men of the coastal communities with current sugarcane and past cotton production, 30% had elevated S-Cr and 19% CDK ≥ stage 3 compared to 4% and 1% in the communities above 500 m with sugarcane, coffee and service-oriented economies. Prevalence of elevated S-Cr among male sugarcane and cotton workers in the coastal lowlands with extremely hard and hot working conditions was 33% vs 4% among sugarcane farmers at 500 m (approximately 4oC lower) and 4% among subsistence farmers. Women followed a weaker but similar pattern. For 10-year increments in coastal sugarcane or cotton plantation work, the occurrence of elevated S-Cr tripled among men and doubled among women. Proteinuria was infrequent and of low grade indicating tubulointerstitial nephropathy.

Conclusions Agricultural work on lowland sugarcane and cotton plantations was associated with CKD among men and women, possibly related to strenuous and hot work with repeated dehydration.