Removing masking factors from urinary rhythm data in humans

Area of Science:

• Chronobiology
• Physiological measurement

Background:

• Circadian rhythms influence body temperature and urinary excretion.
• Previous models separated exogenous and endogenous circadian components for body temperature.
• Urinary data analysis for circadian rhythms requires accounting for external masking factors.

Purpose of the Study:

• To extend a two-component model for separating exogenous and endogenous circadian rhythm components to urinary data.
• To establish normative endogenous urinary data for sodium, potassium, and urate.
• To compare the accuracy of the two-component model versus a one-component model in assessing circadian rhythm adjustment to time zone shifts.

Main Methods:

• Validated a two-component model for urinary sampling formats (overnight and two-hourly samples).
• Collected normative endogenous urinary data from approximately 80 constant routine protocols.
• Simulated an 8-hour eastward time zone transition in 8 subjects to assess model performance.

Main Results:

• The two-component model demonstrated superiority over the one-component model for urinary data, similar to body temperature data.
• Normative endogenous data for urinary sodium, potassium, and urate were established.
• The two-component model's assessment of adjustment rate to a simulated time zone shift was significantly closer to constant routine assessments than the one-component model.

Conclusions:

• The two-component model effectively analyzes urinary data to approximate endogenous circadian rhythm shifts.
• This model provides a more accurate estimation of endogenous rhythm adjustments by mitigating masking effects from exogenous factors.
• The findings support the utility of the two-component model for chronobiological research using urinary biomarkers.