Introduction: Heat exposure associated with climate change has been implicated in recurrent, asymptomatic acute kidney injury, increasing the risk of CKD progression and mortality. However, the relationship between seasonal variation in estimated glomerular filtration rate (eGFR) and clinical outcomes in routine outpatient care in Japan remains unclear. This study aimed to describe seasonal changes in eGFR and to assess the prognostic impact of summer eGFR decline on renal replacement therapy (RRT) initiation and cardiovascular outcomes in regular outpatient settings. Methods: We conducted a retrospective cohort study of adult outpatients who underwent serum creatinine measurement between 2010 and 2023. Seasons were defined by average temperatures in Kanazawa city, Ishikawa, Japan: spring (March-June), summer (July-August), autumn (September-November), and winter (December-February). Seasonal differences in eGFR were estimated using linear mixed-effects models, with spring as the reference. We defined "a summer eGFR decline" as 3. 0 mL/min/1. 73m 2 from spring to summer in the same year since this value was close to the upper threshold of the lowest quartile. Associations between summer eGFR decline and subsequent RRT initiation, cardiovascular events, heart failure hospitalization, and all-cause mortality (30 days) were analyzed using multivariable timedependent Cox proportional hazards models with multiple imputation for missing data. Results: Among 10, 773 patients (46% female, mean age 5320 years, mean eGFR 85. 229. 6 mL/min/1. 73m 2), eGFR significantly decreased in summer (-1. 2 95% CI -1. 3 to -1. 1) and increased in winter (+0. 8 95% CI 0. 7 to 0. 9) compared with spring (both p<0. 01). The median spring-summer eGFR change was -1. 2 (IQR -3. 2 to 1. 1). Patients with summer eGFR decline were older and more likely to have higher baseline eGFR, hypertension, and diabetes. Summer eGFR decline was associated with increased risks of RRT initiation (HR 4. 5 95% CI 2. 9-6. 8, p<0. 001) and heart failure hospitalization (HR 1. 8 95% CI 1. 1-3. 1, p=0. 02), but not cardiovascular events or mortality (p0. 06). Conclusion: In routine outpatient practice, eGFR shows seasonal variation, with summer decline associated with higher risks of RRT initiation and heart failure hospitalization. These findings suggest the potential value of early intervention strategies considering seasonal kidney function changes. I have no potential conflict of interest to disclose. I used generative AI and AI-assisted technologies in the writing process. During the preparation of this work the authors used ChatGPT in order to improve the clarity and fluency of the English text. .
Miyamori et al. (Wed,) studied this question.
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