Efeitos da redução da ingestão de sal sobre a pressão arterial em normotensos, pré-hipertensos e normotensos

Abstract

Introduction: The effects of salt intake reduction on casual blood pressure (BP) among hypertensive patients have been widely studied. However, there are few data about this issue in the context of arterial stiffness, as well as in normotensive and pre-hypertensive subjects. Objective:To evaluate the effects of progressive reduction in intake of the addition salt (from 6 grams / day to 4 grams/day) on peripheral and central pressure values as well as arterial stiffness in normotensive, prehypertensive and hypertensive. Methodology: This is an interventional, single-blind clinical trial, with 13 weeks of follow-up and 4 weeks interval between evaluations, performed with technical-administrative workers and teachers from a public university. Inclusion criteria were age between 20 and 60 years, both genders and which meal at home at least 4 times per week. Exclusion criteria were BP ≥160/100 mmHg, using two or more antihypertensive drugs, secondary hypertension; diabetes, history of myocardial infarction or stroke in the last 6 months, and special need diet. This study was approved by the institution’s Ethics Committee and all the participants signed the informed consent form. Recruitment was performed at the workplace, with a questionnaire about dietary habits, anthropometric and casual BP measurement (OMRON 705CP automatic device). According to the BP levels, participants were classified as normotensive (≤130/85 mmHg), pre-hypertensive (130-139/85-89 mmHg) and hypertensive stage I (≥140- 159/90-99 mmHg). The other evaluated variables were home blood pressure monitoring (HBPM), central blood pressure (CBP) measurement by tonometry (SphygmoCor® system), 24-hour urinarysodium, and dietary salt intake. The participants were instructed to reduce the consumption of foods with high sodium content. The addition of salt used during the follow-up was controlled by delivering individual packages for daily family consumption. The protocol adherence was evaluated by controlling the returned packages at each visit. The data were structured and analyzed using Stata software (version 12). Descriptive analysis was performed using relative and absolute frequencies, as well as median and interquartile range or mean and standard deviation for distribution of categorical and quantitative variables, respectively. For comparison between groups at visit 1, Kruskal-Wallis and Fisher's Exact tests were used. The comparison between the groups was done before and after the intervention using Wilcoxon test and paired Student T test. The correlation between BP values and urinary sodium levels was performed using the Spearman test. For all tests, the significance level was set at 5% and the confidence interval was 95%. Results: Fifty-five participants were evaluated, 32 males (median age 48 years). According to BP values, 18 were normotensive, 15 pre-hypertensive and 22 hypertensive. The salt of addition was reduced at each visit from 6 to 4 g/day. The groups are similar in relation to age and sex. There was no difference between blood pressure measurements and sodium excretion before and after the intervention. The parameters of arterial stiffness also did not suffer. Conclusion: Gradual reduction of addition salt intake in a 13-week follow-up is not able to reduce the loss of danger and mean values of blood pressure.