CARDIOVASCULAR JOURNAL OF AFRICA • Volume 34, No 4, September/October 2023 228 AFRICA diseases, and there are more than 200 million patients with hypertension in China.14 With the social development and changes in lifestyle in recent years, the incidence of hypertension and its related risk factors have increased, and how to effectively control hypertension has become an important public health issue. A high-salt diet is a risk factor for hypertension, stroke and cardiovascular diseases. The association between salt intake and blood pressure variability in 605 patients with hypertension in Ningxia has been studied.15 The results showed that salt intake is an influencing factor for blood pressure variability in hypertensive patients, and reasonable salt restriction is important for controlling both blood pressure and blood pressure variability of patients. Salt sensitivity is susceptible to high salt intake. Jin et al.16 explored the correlation between salt sensitivity and the metabolic syndrome in Gannan Tibetan populations, and found that the detection rate of the metabolic syndrome was higher in salt-sensitive hypertensive and non-hypertensive populations, but the correlation remains to be further confirmed. Ambulatory blood pressure monitoring is a simple, non-invasive examination that can display the patient’s blood pressure at different time points, and also provide the patient’s blood pressure circadian rhythm, blood pressure variability and morning peak blood pressure. The close associations of ambulatory blood pressure monitoring parameters with cardiovascular events and mortality have been confirmed.17 Ambulatory blood pressure monitoring can reflect the 24-hour ambulatory blood pressure, while blood pressure variability can reflect the influence of cardiovascular autonomic nerves on haemodynamics, which is considered a predictor for cardiovascular diseases independent of mean blood pressure.18,19 Cardiovascular events in hypertensive patients are not only related to blood pressure control level, but also closely related to blood pressure variability. The increase in blood pressure variability may lead to target-organ damage in hypertensive patients and its changes have attracted increasing attention in clinical treatment of hypertension.20 Wu et al.21 conducted screening for cardiovascular diseases among residents in six districts/counties in three towns and three villages in Liaoning Province, and explored the influencing factors for cardiovascular diseases. They found that the high-risk rate of cardiovascular diseases increased with age. In another study,22 cohort analysis was conducted on the clinical data of 985 patients with essential hypertension, and the results showed that 15 factors, including family history of cardiovascular diseases, were associated with major cardiovascular events. Cardiovascular diseases have a certain genetic tendency, and inquiring about the family history of cardiovascular diseases is helpful for predicting the risk of cardiovascular diseases in patients with essential hypertension. The clinical indices of 382 patients with essential hypertension were analysed in the literature, and the levels of angiotensin and aldosterone were compared among patients with different grades of salt-sensitivity risk. The results revealed that the high-risk group had an increased level of aldosterone and a decreased level of angiotensin, further worsening target-organ damage in hypertensive patients.23 Moreover, 1 277 patients with essential hypertension were subjected to cardiovascular risk stratification, and ambulatory blood pressure monitoring parameters were compared in different groups. It was found that ambulatory blood pressure-monitoring parameters were correlated with the cardiovascular risk stratification of patients with essential hypertension, and four parameters, including night-time systolic standard deviation, were helpful for cardiovascular risk stratification of patients with essential hypertension.24 Wang et al.25 divided, by detecting 24-hour heart rate and blood pressure circadian rhythm, 315 patients with essential hypertension into low-, medium- and high-risk groups and 1.00 0.90 0.75 0.50 0.25 0.10 0.00 0.00 0.10 0.25 0.50 0.75 0.90 1.00 1 – Specificity Sensitivity Fig. 1. ROC curve of risk factors for cardiovascular events in patients with essential hypertension. Table 5. Cox multivariate linear regression analysis results of cardiovascular risk in patients with essential hypertension Independent variable B SE Wald p-value HR (95% CI) Age 1.179 0.247 11.253 0.041 2.146 (1.603–3.588) Family history of cardiovascular diseases 2.163 0.352 15.982 0.026 3.589 (1.960–5.026) Salt-sensitivity risk stratification 1.687 0.309 13.927 0.033 3.015 (1.792–4.163) Low-density lipoprotein cholesterol 0.129 0.358 0.743 0.596 1.153 (1.023–1.619) Standard deviation of sequential 5-minute normal-to-normal interval 0.492 0.472 1.659 0.079 1.119 (0.936–1.258) 24-h heart rate 0.671 0.598 0.533 0.317 1.026 (0.985–1.358) Night-time systolic standard deviation 1.586 0.636 16.742 0.013 4.569 (2.378–5.932) 24-h systolic standard deviation 1.231 0.821 15.683 0.025 3.651 (1.985–4.392) 24-h systolic blood pressure coefficient of variation 0.517 0.769 2.858 0.046 1.208 (1.106–2.536) Age: ≥ 55 years: 1, < 55 years: 0; family history of cardiovascular diseases: yes: 1, no: 0; salt sensitivity: high risk: 1, medium and low risk: 0; low-density lipoprotein cholesterol: ≥ 3.5 mmol/l: 1, < 3.5 mmol/l: 0; standard deviation of sequential five-minute normal-to-normal interval: < 50 ms: 1, ≥ 50 ms: 0; 24-h heart rate: < 62 beats/ min: 1, ≥ 62 beats/min: 0; night-time systolic standard deviation: ≥ 14 mmHg: 1, < 14 mmHg: 0; 24-h systolic standard deviation: ≥ 20 mmHg: 1, < 20 mmHg: 0; 24-h systolic blood pressure coefficient of variation: ≥ 13.5%: 1, < 13.5%: 0.
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