Physical Activity and Urinary Sodium Excretion Circadian Rhythm: A Population-Based Cross-Sectional Pilot Study

Area of Science:

• Cardiovascular Physiology
• Renal Physiology
• Chronobiology

Background:

• Blood pressure (BP) exhibits a circadian rhythm with nocturnal dipping, a pattern linked to cardiovascular disease (CVD) risk.
• Circadian rhythm of urinary sodium excretion (NaCle) correlates with BP patterns, peaking during daytime.
• Physical activity (PA) improves BP control and dipping, but its effect on NaCle rhythm is unknown.

Purpose of the Study:

• To investigate the correlation between physical activity (PA) and the circadian rhythm of urinary sodium excretion (NaCle).
• To determine if this relationship is independent of age, sex, BP, dipping status, and salt intake.

Main Methods:

• Pilot cross-sectional analysis of 953 participants from the Ticino Epidemiological Stiffness Study.
• Data collected via questionnaires, blood samples, 24-hour urine collections, and ambulatory BP monitoring.
• Participants categorized by PA levels (sedentary, partially active, active); multivariable linear regressions used to assess PA, NaCl intake, and dipping effects on day/night NaCle ratio.

Main Results:

• The day/night NaCle ratio positively correlated with the dipping pattern.
• Physical activity (PA) did not show a significant correlation with the NaCle ratio.
• Higher salt intake correlated with increased BP, particularly in men and younger individuals.

Conclusions:

• The day/night NaCle ratio is linked to the BP dipping pattern, but PA is not associated with the circadian rhythm of renal sodium handling.
• The cardiovascular benefits of PA appear to be mediated through mechanisms independent of NaCle circadian rhythm.
• Further research is warranted to elucidate the specific pathways through which PA impacts BP and cardiovascular health.