Population-level circadian rhythm of eGFR and the effect of chronodisruption.

Chronic kidney disease (CKD) is one of the leading causes of global morbidity, and early diagnosis is essential to prevent complications. Estimated glomerular filtration rate (eGFR) is a key biomarker for assessing renal function. However, its value is influenced by various factors, including circadian variations. Previous studies have documented a circadian rhythm in eGFR, but population-level investigations using the cosinor method have not been conducted. We conducted a retrospective study in two hospitals in Spain (Toledo and Lorca) between 2017 and 2019. The circadian rhythm of eGFR was studied by fitting it to a cosine function, analyzing the effects of age and CKD stage. The results showed a statistically significant circadian rhythm in both populations, with the acrophase occurring at the beginning of the active phase of the day. The amplitude of the rhythm decreased in older patients (70-85 yr), whereas patients with advanced CKD had lost their circadian rhythm entirely. This study, for the first time, uses the cosinor method to demonstrate the existence of a population-level circadian rhythm of eGFR. The cosinor analysis was performed on different CKD stages and ages, revealing the existence of significant rhythms, although none at advanced ages or post-G1 CKD stage. The loss of circadian variability in advanced CKD emphasizes the importance of considering these rhythms in clinical practice to improve the diagnosis and management of kidney disease.NEW & NOTEWORTHY This study, for the first time, uses the cosinor method to demonstrate the existence of a population-level circadian rhythm of estimated glomerular filtration rate, which is influenced both by age and the progression of chronic kidney disease.