Association between Dietary Sodium Intake and Blood Pressure Variability in Chinese Patients with Hypertension

Association between Dietary Sodium Intake and Blood Pressure Variability in Chinese Patients with Hypertension

Hypertension is a significant risk factor for cardiovascular morbidity and mortality, with elevated blood pressure (BP) strongly linked to an increased risk of cardiovascular events. Blood pressure variability (BPV), which measures fluctuations in BP, is also associated with heightened cardiovascular risk, independent of BP levels. While the effects of antihypertensive drugs on stroke risk have been studied in relation to intra-individual BPV, few studies have explored the predictors of BPV itself. High dietary sodium intake is a well-known independent risk factor for cardiovascular events and significantly increases BP levels in hypertensive patients. However, the relationship between sodium intake and BPV remains controversial, particularly in Chinese hypertensive populations. This study aims to investigate the association between dietary sodium intake and BPV in Chinese patients with hypertension.

The study enrolled 235 patients with essential hypertension from the Department of Cardiology, Chinese People’s Liberation Army (PLA) General Hospital between 2018 and 2019. All participants underwent 24-hour ambulatory blood pressure monitoring (ABPM). BPV was calculated using the standard deviation (SD), coefficient of variation (CV), and variation independent of mean (VIM) of BP measurements. These metrics were further divided into diurnal systolic BPV (SBPV), diurnal diastolic BPV (DBPV), nocturnal SBPV, and nocturnal DBPV. Dietary sodium intake was assessed through 24-hour urine sodium excretion, which is considered the gold standard for measuring sodium intake. The relationship between dietary sodium intake and BPV was analyzed using Spearman correlations and multiple linear regression analysis.

The results revealed that nocturnal SBPV-SD, CV, VIM, and nocturnal DBPV-SD were significantly higher in the high urine sodium excretion group compared to the medium and low sodium excretion groups. In contrast, diurnal SBPV-SD, CV, VIM, diurnal DBPV-SD, CV, VIM, and nocturnal DBPV-CV, VIM did not show significant differences among the groups. Spearman correlation analysis indicated a linear relationship between 24-hour urine sodium excretion and nocturnal SBPV-SD, CV, VIM (SD, r = 0.22, P = 0.001; CV, r = 0.17, P = 0.009; VIM, r = 0.16, P = 0.020), as well as nocturnal DBPV-SD (r = 0.21, P = 0.001). Multiple linear regression analysis, after adjusting for confounding factors such as age, gender, body mass index (BMI), nocturnal average SBP, nocturnal average DBP, nocturnal average heart rate (HR), fasting blood glucose (FBG), triglycerides (TG), total cholesterol (TC), serum potassium, serum sodium, estimated glomerular filtration rate (eGFR), smoking status, drinking status, antihypertensive medication use, albuminuria, and reverse-dipper BP, confirmed these positive correlations (nocturnal SBPV-SD, β = 0.224, P < 0.001; nocturnal SBPV-CV, β = 0.211, P = 0.001; nocturnal SBPV-VIM, β = 0.213, P = 0.001; nocturnal DBPV-SD, β = 0.215, P = 0.001).

A sensitivity analysis excluding participants with albuminuria (n = 208) yielded similar results, with 24-hour urine sodium excretion independently related to nocturnal SBPV-SD, CV, VIM, and nocturnal DBPV-SD. Subgroup analysis further demonstrated that the associations between 24-hour urine sodium excretion and nocturnal SBPV-SD, CV, VIM, and nocturnal DBPV-SD were more pronounced in participants with reverse-dipper BP (n = 93). In contrast, these associations were less significant in participants without reverse-dipper BP (n = 142).

The study’s findings suggest that dietary sodium intake is a robust predictor of elevated nocturnal SBPV in Chinese hypertensive patients, particularly in those with reverse-dipper BP. This relationship may be attributed to the modulation of sympathetic nerve activity by high sodium intake, as previous studies in rats have shown that sodium affects the central gain of sympathetic circuits, thereby increasing BPV. Additionally, hypertensive patients with reverse-dipper BP patterns are more likely to be salt-sensitive, with higher nocturnal sodium excretion rates, which may explain the stronger correlation in this subgroup.

The study has several strengths, including the use of strict diagnostic criteria for hypertension, precise measurement of 24-hour urine sodium excretion, and controlled conditions during hospitalization to minimize external factors affecting sodium excretion and BPV. However, there are limitations to consider. The cross-sectional design does not allow for the determination of causal relationships between high sodium intake and elevated nocturnal SBPV. Additionally, the sample size may have limited the detection of significant differences in CV and VIM of nocturnal DBPV among the sodium excretion groups. Future large-scale, multi-center prospective intervention studies are needed to further explore these relationships.

In conclusion, this study highlights the association between dietary sodium intake and nocturnal SBPV in Chinese hypertensive patients, particularly in those with reverse-dipper BP. These findings underscore the importance of monitoring and potentially reducing sodium intake to manage BPV and mitigate cardiovascular risk in this population.

doi.org/10.1097/CM9.0000000000000740

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