Diurnal rhythms of urine volume and electrolyte excretion in healthy young men under differing intensities of daytime light exposure

Abstract

In humans, most renal functions, including urine volume and electrolyte excretions, have a circadian rhythm. Light is a strong circadian entrainment factor and daytime-light exposure is known to affect the circadian rhythm of rectal temperature (RT). The effects of daytime-light exposure on the diurnal rhythm of urinary excretion have yet to be clarified. The aim of this study was to clarify whether and how daytime exposure to bright-light affects urinary excretions. Twenty-one healthy men (21–27 years old) participated in a 4-day study involving daytime (08:00–18:00 h) exposure to two light conditions, Dim (< 50 lx) and Bright (~ 2500 lx), in a random order. During the experiment, RT was measured continuously. Urine samples were collected every 3 ~ 4 h. Compared to the Dim condition, under the Bright condition, the RT nadir time was 45 min earlier (p = 0.017) and sodium (Na), chloride (Cl), and uric acid (UA) excretion and urine volumes were greater (all p < 0.001), from 11:00 h to 13:00 h without a difference in total daily urine volume. The present results suggest that daytime bright light exposure can induce a phase shift advance in urine volume and urinary Na, Cl, and UA excretion rhythms.

The role of renal circadian biorhythms in lifelong LUTS

“…While limited data exists on its effects in children, a recent study by Nakamoto et al in young adults demonstrated that daytime light exposure can affect diurnal rhythms of urine volume and urinary sodium/chloride concentrations. This suggests that light exposure can disrupt the rhythm of urinary excretion 13 …”

Risk analyses of nocturia on incident poor sleep and vice versa: the Nagahama study

“…Appropriate guidance and medications should be provided while behavior and lifestyle modifications, such as fluid/caffeine restriction and leg elevation in the evening, stockings for peripheral edema, pelvic floor muscle training, delayed voiding, and urge suppression 26 may be useful. Additionally, clear circadian boundaries in activities, such as exercise in the evening 27 , taking a bath 1–2 h before bedtime 28 , and light exposure in the morning 29 could reduce nocturnal urination and may prevent incident poor sleep and disruption of deep sleep, thereby extending healthy life expectancy. Desmopressin administration to patients with nocturnal polyuria has additionally been shown to significantly improve both nocturia and the duration of the first sleep period 30 .…”