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Heat exposure induces diurnal differences in renal responses, with daytime heat affecting glomerular filtration markers and nighttime heat elevating early kidney stress biomarkers.

In a randomized crossover trial, 41 healthy adults exposed to 8 hours of heat showed distinct renal biomarker changes depending on time of day. Daytime heat increased serum creatinine by 7.67% and cystatin C by 3.05%, while nighttime heat increased urinary IGFBP-7 by 58.40%, KIM-1 by 47.25%, and TIMP-2 by 51.88%. Sleep-related parameters partially mediated nighttime heat effects on renal responses.

Last updated: Aug 26, 2026•1 RCTs•📖 Read as article →

Evidence Score

Evidence Score44/100
Human RCT★★☆☆☆
Meta-analysis☆☆☆☆☆
Mechanism★★★★★
Safety★★★★☆
Confidencelow

Study Evidence

Study 1. Diurnal Differences in the Effects of Heat Exposure on Renal Function: A Randomized Controlled Crossover Trial.

observational

Liu J, Li Y, Fan Y, Zou X, Ho HC, Zhang D, Zhang J, Song J, Wang X, Ding X, Jin X, Qiu L, Tong S, Su H, Fan Y, Huang C, Cheng J · Environmental research (2026)

Participants: N/A
Duration: 8 hours per exposure
Intervention: 8-hour exposure to heat (32°C daytime, 30°C nighttime) vs thermoneutral (26°C) in a controlled laboratory setting
Outcome: Renal biomarkers: serum creatinine, cystatin C, eGFR, urinary IGFBP-7, KIM-1, TIMP-2; sleep quality, duration, heart rate variability
Effect Size: Daytime: creatinine +7.67% (95% CI 4.73-10.61), cystatin C +3.05% (95% CI 0.17-5.93); Nighttime: IGFBP-7 +58.40% (95% CI 27.66-89.14), KIM-1 +47.25% (95% CI 18.91-75.59), TIMP-2 +51.88% (95% CI 22.26-81.51)
Population: 41 healthy adults

Result:

PubMed: 42637191DOI: 10.1016/j.envres.2026.125547

Mechanism Graph

Heat exposure triggers physiological stress responses affecting renal function
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Daytime heat primarily impacts glomerular filtration, increasing serum creatinine and cystatin C while reducing eGFR
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Nighttime heat predominantly activates tubular injury and early kidney stress pathways, increasing urinary IGFBP-7, KIM-1, and TIMP-2
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Sleep-related parameters (quality, duration, HRV) partially mediate nighttime heat effects on renal responses

Limitations

  • ⚠Only healthy adults studied; results may not generalize to vulnerable populations (e.g., elderly, those with chronic kidney disease)
  • ⚠Controlled laboratory conditions may not reflect real-world heat exposure patterns (e.g., intermittent heat, humidity, physical activity)
  • ⚠Short-term exposure (8 hours) may not capture long-term renal effects of chronic heat exposure

Frequently Asked Questions

Does heat exposure affect kidney function differently at night compared to daytime?▼

Yes, this study found that daytime heat primarily affects blood markers of glomerular filtration (creatinine, cystatin C, eGFR), while nighttime heat predominantly elevates urinary biomarkers of early kidney stress (IGFBP-7, KIM-1, TIMP-2).

What are the key renal biomarkers measured in this study?▼

The study measured serum creatinine, cystatin C, estimated glomerular filtration rate (eGFR), and urinary insulin-like growth factor-binding protein 7 (IGFBP-7), kidney injury molecule-1 (KIM-1), and tissue inhibitor of metalloproteinases-2 (TIMP-2).

How large were the effects of heat on renal biomarkers?▼

Daytime heat increased creatinine by 7.67% and cystatin C by 3.05%, while nighttime heat increased IGFBP-7 by 58.40%, KIM-1 by 47.25%, and TIMP-2 by 51.88%.

What is the clinical significance of these findings?▼

The findings suggest that nighttime heat exposure may be particularly harmful to kidney health, as it triggers early kidney stress markers. This is relevant given increasing nighttime temperatures due to climate change.

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References

  1. 1.Liu J, Li Y, Fan Y, Zou X, Ho HC, Zhang D, Zhang J, Song J, Wang X, Ding X, Jin X, Qiu L, Tong S, Su H, Fan Y, Huang C, Cheng J. "Diurnal Differences in the Effects of Heat Exposure on Renal Function: A Randomized Controlled Crossover Trial.." Environmental research, 2026. PMID: 42637191 DOI: 10.1016/j.envres.2026.125547
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