What is the clinical evidence from this study?

Study design: Cross-Sectional. Population: Chronic kidney disease (n=130). Intervention: Nocturnal hypertension vs. Without nocturnal hypertension. Primary outcome: Nighttime urine sodium excretion (mEq) (p=0.012).

What does this research mean for the field?

In patients with chronic kidney disease, increased nighttime urine sodium excretion is closely linked to higher nighttime blood pressure, nocturnal hypertension, and more frequent nocturia, independent of total sodium excretion. Novelty: ClaimNovelty.CONFIRMATORY. Consensus alignment: ConsensusAlignment.NEUTRAL.

What question did this study set out to answer?

This study aims to explore the relationship between sodium excretion patterns and blood pressure regulation in patients with chronic kidney disease.

June 3, 2026

Nighttime and Daytime Urine Sodium Excretion, Nighttime and Daytime Blood Pressure and Nocturia Frequency in Patients With Chronic Kidney Disease

Key Result

In patients with CKD, nocturnal hypertension was associated with significantly higher nighttime urine sodium excretion (64.0 vs 49.7 mEq, P=0.012) and more frequent nocturia.

Key Points

This study aims to explore the relationship between sodium excretion patterns and blood pressure regulation in patients with chronic kidney disease.
130 patients with CKD stages 1–5 underwent 24-h ambulatory BP monitoring and split urine collection.
Patients were classified by tertiles of nighttime-to-daytime sodium excretion ratio and presence of nocturnal hypertension.
Comparative analysis of sodium excretion, blood pressure, and nocturia frequency was conducted.
Nighttime systolic blood pressure (SBP) and diastolic blood pressure (DBP) showed significant increases across tertiles of nighttime-to-daytime sodium excretion (p=0.047/p=0.014).
Patients with nocturnal hypertension had increased nighttime urine sodium excretion (64.0±34.5 vs. 49.7±23.9 mEq, p=0.012) and nocturia frequency (2.0 vs. 1.0, p=0.006).
Nighttime sodium excretion correlated positively with nighttime SBP (r=0.212, p=0.016) and DBP (r=0.320, p<0.001).

Study Design

Type

Cross-Sectional (n=130)

Structured PICO

Does increased nighttime urine sodium excretion correlate with nocturnal hypertension and nocturia in patients with chronic kidney disease?

Population

130 patients with CKD stages 1-5 on stable antihypertensive treatment evaluated with 24-hour ambulatory blood pressure monitoring and split urine collection.

Outcome

Differences in daytime/nighttime blood pressure, dipping, and nocturia frequencysurrogate

In patients with CKD, increased nighttime natriuresis is significantly associated with higher nighttime blood pressure and nocturnal hypertension, independent of total sodium excretion.

Main Result

Absolute Event Rate: 64% vs 49.7%

p-value: p=0.012

Abstract

Objective: Abnormal circadian blood pressure (BP) regulation is common in chronic kidney disease (CKD), with nighttime BP being a strong predictor of cardiovascular events and mortality. Normal renal sodium handling follows a circadian pattern with greater daytime sodium excretion. In the general population and hypertensive patients, higher nighttime natriuresis, is linked to elevated nighttime BP, but detailed evidence in CKD patients is scarce. This study examined differences in daytime/nighttime BP, dipping and nocturia frequency between CKD patients classified by nighttime-to-daytime urine sodium excretion ratio and differences in diurnal sodium excretion and nocturia between CKD patients with and without nocturnal hypertension. Design and method: 130 patients with CKD stages 1–5 on stable antihypertensive treatment underwent 24-h ambulatory BP monitoring with the ABPMpro device and simultaneous split 24-h urine collection separated into daytime (7:00-23:00) and nighttime (23:00-7:00) periods. For analyses, patients were divided by tertiles of nighttime-to-daytime ratio of urine sodium excretion and by presence of nocturnal hypertension. Results: No significant differences were detected in baseline characteristics across groups of nighttime-to-daytime sodium excretion ratio. In contrast to daytime SBP/DBP (T1: 124.8±10.1/70.6±7.9 vs. T2: 128.3±12.2/74.6±8.6 vs. T3: 128.6±12.8/73.6±8.2 mmHg, p=0.254/p=0.072 respectively), nighttime SBP and DBP (117.1±12.0/64.8±6.9 vs. 121.7±13.1/68.7±7.6 vs. 123.8±13.1/69.3±8.1 mmHg, p=0.047/p=0.014 respectively) showed significant increases across tertiles of nighttime-to-daytime sodium excretion When patients with and without nocturnal hypertension were compared, those with nocturnal hypertension had similar daytime (83.8±45.9 vs. 87.6±50.6 mEq, p=0.654), but higher nighttime urine sodium excretion (64.0±34.5 vs. 49.7±23.9 mEq, p=0.012), higher nighttime-to-daytime sodium excretion ratio (0.73 0.53 vs. 0.57 0.63, p=0.037) and more frequent nocturia (2.0 2.0 vs. 1.0 2.0, p=0.006). Nighttime sodium excretion correlated with nighttime SBP (r=0.212, p=0.016) and DBP (r=0.320, p<0.001), while daytime sodium excretion did not. Conclusions: In CKD, impaired circadian renal sodium handling, characterized by increased nighttime natriuresis, is closely linked to higher nighttime BP and nocturnal hypertension, independent of total sodium excretion. Assessment of nighttime urine sodium excretion may help identify sodium-dependent nocturnal hypertension and guide targeted therapeutic strategies.

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