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Updated: May 28, 2026

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Published on: November 11, 2016
Circadian Modulation of Protein Catabolism: Insight from a Population Study
Miriam Lisa Kafader1, Sébastien Sare2, Martina Zandonà2
1Faculty of Biomedicine, Università della Svizzera Italiana, 6900 Lugano, Switzerland.
Background/Objectives:
Urinary urea excretion is a marker of protein catabolism and follows circadian biological rhythms. Although small-scale studies have suggested a diurnal pattern, its population-level characterisation and determinants remain poorly defined.
Methods:
This cross-sectional study was conducted within the Ticino Epidemiological Stiffness Study (TEST-study), a population-based cross-sectional analysis of 1202 adults (≥18 years) recruited in the Italian-speaking region of Switzerland in 2017-2018. A final analytical sample of 859 participants provided 24 h urine collections divided into diurnal and nocturnal fractions, from which a day-to-night (Day/Night) urea excretion ratio was calculated as the primary outcome. Multivariable linear regression was used to identify independent determinants.
Results:
Across the cohort, a predominant nocturnal pattern of urinary urea excretion was observed, with a mean Day/Night ratio below 1. In younger women (<40 years), the ratio approached 1, indicating an attenuated Day/Night pattern, whereas older women (>65 years) displayed a significantly more pronounced nocturnal predominance. No comparable age-related trend was observed in men. In multivariable analysis, advancing age, greater nocturnal blood pressure dipping, and higher sodium excretion were independently associated with the Day/Night urea ratio.
Conclusions:
Urinary urea excretion, a surrogate marker of protein catabolism, exhibits a measurable Day/Night variation, associated with age, sex, and hemodynamic factors. These findings provide insights for chrononutritional strategies aimed at preserving muscle health across lifespan.
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