Heat stress, hydration and uric acid: a cross-sectional study in workers of three occupations in a hotspot of Mesoamerican nephropathy in Nicaragua

Abstract

ObjectivesTo study Mesoamerican nephropathy (MeN) and its risk factors in three hot occupations.DesignCross-sectional.SettingChinandega and León municipalities, a MeN hotspot on the Nicaraguan Pacific coast, January–February 2013.Participants194 male workers aged 17–39 years: 86 sugarcane cutters, 56 construction workers, 52 small-scale farmers.Outcome measures(1) Differences between the three occupational groups in prevalences/levels of socioeconomic, occupational, lifestyle and health risk factors for chronic kidney disease (CKD) and in biomarkers of kidney function and hydration; (2) differences in prevalences/levels of CKD risk factors between workers with reduced estimated glomerular filtration rate (eGFRCKD-EPI <80 mL/min/1.73 m2) and workers with normal kidney function (eGFRCKD-EPI ≥80 mL/min/1.73 m2).ResultsSugarcane cutters were more exposed to heat and consumed more fluid on workdays and had less obesity, lower blood sugar, lower blood pressure and a better lipid profile. Reduced eGFR occurred in 16%, 9% and 2% of sugarcane cutters, construction workers and farmers, respectively (trend cane > construction > farming, p=0.003). Significant trends (cane > construction > farming) were also observed for high serum urea nitrogen (blood urea nitrogen (BUN) >20 mg/dL), high serum creatinine (SCr >1.2 mg/dL), low urinary pH (≤5.5) and high BUN/SCr ratio (>20) but not for high urinary specific gravity (≥1.030). Sugarcane cutters also more often had proteinuria and blood and leucocytes in the urine. Workers with eGFR <80 mL/min/1.73 m2 reported a higher intake of water and lower intake of sugary beverages. Serum uric acid levels related strongly and inversely to eGFR levels (adj β −10.4 mL/min/1.73 m2, 95% CI −12.2 to −8.5, p<0.001). No associations were observed for other metabolic risk factors, pesticides, non-steroidal anti-inflammatory drugs or alcohol. Among cane cutters, consumption of electrolyte hydration solution appeared preventive (adj β 8.1 mL/min/1.73 m2, p=0.09).ConclusionsHeat stress, dehydration and kidney dysfunction were most common among sugarcane cutters. Kidney dysfunction also occurred to a lesser extent among construction workers, but hardly at all among small-scale farmers. High serum uric acid was associated with reduced kidney function.

Rationale, description and baseline findings of a community-based prospective cohort study of kidney function amongst the young rural population of Northwest Nicaragua

“…Using questionnaires (modified from those previous studies [1, 11, 17, 18]) exposure data were collected on heat stress, recurrent dehydration, physically demanding work, workplace conditions, pesticide exposure and potential exposure to heavy metals.…”

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“…The recent renaissance in interest in water and its relationship with vasopressin in patients with chronic kidney disease is largely due to two relatively recent discoveries, (i) of an antagonist for antidiuretic hormone action, which is well tolerated and (ii) a stable assay of a surrogate for vasopressin, copeptin, which makes it much easier to assess its action in experiments in animals and man [33,34]. This section focuses on the role of water in preventing chronic kidney disease progression although there is strong evidence for a role in autosomal dominant polycystic kidney disease, reviewed in the next section, renal calculi and heat stress nephropathy, among other renal conditions [35][36][37][38][39][40][41][42][43][44][45][46].…”

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