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. 2025 Jul 1:276:121420.
doi: 10.1016/j.envres.2025.121420. Epub 2025 Mar 18.

Association between objectively assessed physical activity and kidney function among female agricultural workers in hot environments in Spain

Sarah Koch  1 , Joren Buekers  2 , Ana Espinosa  3 , Juan Gómez-Salgado  4 , Gabriel Pombo  5 , Loes Werkman  6 , Lourdes Arjona  3 , Ali Al Rashed  7 , Ben Caplin  7 , Manolis Kogevinas  3 , Francisco Brocal-Fernandez  8 , Amin Oomatia  7 , Neil Pearce  9 , Oriana Ramirez-Rubio  10 , Carlos Ruíz-Frutos  4 , Judith Garcia-Aymerich  2 , Cristina O'Callaghan-Gordo  11
Affiliations

Association between objectively assessed physical activity and kidney function among female agricultural workers in hot environments in Spain

Sarah Koch et al. Environ Res. .

Abstract

Background: Physical activity in hot environments has been associated with impaired kidney function. We aimed to quantify the association between occupational physical activity and kidney function over one work shift in female agricultural workers exposed to environmental heat.

Methods: We measured occupational physical activity in female berry pickers in Huelva, Spain, using movement intensity, based on vector magnitude units (VMU), and heart rate (HR). For both, we calculated the mean (VMU_mean; HR_mean), standard deviation (VMU_sd; HR_sd), and 3-min 95th percentile (VMU_p95; HR_p95). Environmental heat in greenhouses was estimated using wet bulb globe temperature (WBGT). Kidney function and injury were quantified using pre- and post-shift differences in serum creatinine (SCr_dif), Cystatin C (Cystatin C_dif) and neutrophil gelatinase associated lipocalin (NGAL_dif), respectively. Acute Kidney Injury (AKI) was defined as an increase in post-shift serum creatinine of ≥0.3 mg/dl, or ≥1.5 times pre-shift levels. Heat strain was estimated using the ISO 7933:2004 index. We used linear and logistic regressions.

Results: Ninety women aged 37.4 ± 5.7 years were exposed to a mean WBGT of 25.2 (±3.6)°C and light intensity physical activity (HR_mean of 94 (±9)bpm). Of those, 26 % experienced heat strain, 68 % were dehydrated, and 7 % presented with AKI at the end of the shift. Higher VMU_sd was associated with higher Scr_dif (β: 0.029 (95 % CI: 0.00; 0.058) and meeting the threshold for AKI (OR: 1.6 (95 % CI: 0.8; 3.2)). We observed higher NGAL_dif with higher VMU_mean (β: 1.944 (95 % CI: 0.139; 3.748)) per 100 VMU_mean increase. The positive association between HR_mean and SCr_dif was stronger among women with heat strain (interaction p = 0.033).

Conclusions and relevance: In female harvest workers, high means and variations in VMU over a single one shift worked under hot conditions were associated with kidney injury, as assessed by urinary biomarkers, though there is limited evidence for any change in kidney function. Precautiously, large changes in physical activity intensity over one work shift should be avoided to protect from renal injury.

Keywords: Acute kidney injury; Dehydration; Environmental heat; Heat strain; Occupational physical activity; Wearable monitoring.

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Conflict of interest statement

Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: We list below the funding agencies that have funded the project and awarded co-authors fellowships that covered their salaries while working on this manuscript. This study has been funded by the Carlos III Health Institute (project PI17/01555) and co-financed by the European Union (FEDER) “A way to make Europe”. SK (IJC2020-044363-I) and JB (FJC2021-046458-I) received funding from the Juan de la Cierva Incorporacion and Iniciacion, respectively, Fellowships of the Spanish Ministry of Research and Innovation. We acknowledge support from the Spanish Ministry of Science and Innovation and State Research Agency through the “Centro de Excelencia Severo Ochoa 2019–2023” Program (CEX2018-000806-S), and the grant CEX2023-0001290-S funded by MCIN/AEI/10.13039/501100011033, in addition to support from the Generalitat de Catalunya through the CERCA Program. Neil Pearce and Ben Caplin's involvement was supported by a Programme Grant (MR/V033743/1) from the UK Medical Research Council (MRC/UKRI). All other authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.