Dipping in Ambulatory Blood Pressure Monitoring Correlates With Overnight Urinary Excretion of Catecholamines and Sodium

Abstract

Nondipping blood pressure (BP) is associated with increased morbidity and mortality. This study examines the relationship of "dipping" in 24-hour ambulatory BP monitoring (ABPM) with awake and sleeping urinary norepinephrine (NE) and epinephrine (EPI), and that of urinary NE and EPI with urinary sodium (UNa). Fifty nondippers and 65 dippers were included in the present study. Collected data included age, sex, body mass index, history of hypertension, current antihypertensive treatment, ABPM data, and NE, EPI, and UNa values. Hierarchical multiple regression analysis with the night-to-day ratio (NDR) of systolic BP as a dependent variable showed that the composite term of the NDRs of urinary NE and EPI was a significant predictor for dipping. Results also show a differential role of NE and EPI in circadian UNa excretion in dippers and nondippers. These results indicate that the sympathetic nervous system is involved in the regulation of circadian BP variations and UNa excretion.

Figure 1

Relationship of the dip in systolic blood pressure (NDR SBP) with the dip in the composite term of norepinephrine and epinephrine (NDR [NE×EPI]). Significance of Spearman's coefficient of correlation is denoted.

Figure 2

Relationship of the night‐to‐day ratio of total sodium excretion (NDR total Na) with the night‐to‐day ratio of total norepinephrine (NDR total NE) (A and B) and epinephrine (NDR total EPI) (C and D) excretion for dippers (A and C) and nondippers (B and D), respectively. Significances of Spearman's coefficients of correlation are denoted.

Figure 3

Relationship of the 24‐hour total sodium excretion (24h Na [mmol/d]) with the 24‐hour total NE (24h NE [μmol/d]) (A and B) and EPI (24h EPI [μmol/d]) (C and D) excretion for dippers (A and C) and nondippers (B and D), respectively. Significances of Spearman's coefficients of correlation are denoted.