Heat Stress and Kidney Injury in Taiwanese Farmers: Associations With Renal Artery Resistance and Urinary Acidification.

RATIONALE &

OBJECTIVE

Taiwan has the world's highest burden of end-stage kidney disease, and farmers face elevated risk of chronic kidney disease of nontraditional causes (CKDnt). This study explored mechanisms linking heat stress to acute kidney injury (AKI) among agricultural workers.

STUDY

DESIGN

Pre-post study with repeated measures.

SETTING &

PARTICIPANTS

119 agricultural workers in Taiwan (2023-2024).

EXPOSURE: Occupational heat stress characterized by the physiological strain index (PSI).

OUTCOME: Pre- and post-work shift serum creatinine; urine biomarkers, including monocyte chemotactic protein-1 (MCP-1), N-acetyl-β-d-glucosaminidase (NAG), and 8-hydroxy-2'-deoxyguoanosine (8-OHdG); and the renal artery resistance index (RI). AKI was defined as a rise in post-shift serum creatinine of ≥0.3 mg/dL.

ANALYTICAL APPROACH: Difference-in-differences (DID) analysis to evaluate biomarker changes by AKI status.

RESULTS

AKI occurred in 24 participants (20.2%) and was associated with higher peak core temperature and lower post-shift urinary pH (both P = 0.02). Higher PSI was associated with greater declines in estimated glomerular filtration rate (β = -1.27; P = 0.01). After a single workday under heat stress, the AKI group showed significant increases in urinary NAG/specific gravity (P = 0.008), MCP-1/specific gravity (P = 0.002), and RI (P = 0.03). The DID analysis demonstrated a significantly higher increase in urine NAG (P = 0.04) and MCP-1 (P = 0.001) in the AKI group. Urine acidification was significantly associated with increases in MCP-1/specific gravity (P < 0.001).

LIMITATIONS: No information on the persistence of kidney dysfunction after acute declines in post-work kidney function.

CONCLUSIONS

Heat stress was associated with AKI accompanied by elevated core temperature, inflammation, urine acidification, and renal ischemia, suggesting potential mechanisms underlying heat-related acute declines in kidney function.

PLAIN-LANGUAGE SUMMARY: Outdoor workers face increasing risks to their kidney health as global temperatures continue to rise. In this study, agricultural workers were followed during a typical summer workday to examine how heat stress affected their kidneys. Before and after work, we measured their physical strain, renal artery resistance, kidney function, and several blood and urine biomarkers. We found that heat exposure was associated with impaired kidney function, urinary acidification, and inflammation. These results underscore the need for stronger protection, monitoring, and education for people working in hot environments as extreme heat events become more frequent.