Effects Of Salt Substitution On Blood Pressure Using Office, Home And Ambulatory Measurements In Hypertensive Patients And Their Families: A Double-blinded Randomized Controlled Trial

Objects:To evaluate the long-term antihypertensive effects of salt substitution in hypertensive patients and their families and its safety and feasibility.Methods:A randomized double-blinded controlled trial was conducted.A total of 220 hypertensive patients as indicated case and 348 families took part in this study.The regular salt or salt substitution was randomizedly allocated to two groups during one year. For the indicated cases,office and home blood pressure were measured at baseline,3 months,6 months and 12 months,and ambulatory blood pressure was monitored at baseline and 12 months.Blood sampled at baseline,3months and 12months to measure serum creatinine,urea nitrogen,sodium and potassium for the safety evaluation.Spot morning urine samples were collected to measure urine sodium and potassium,and taste were evaluated by the Visual Analogue Scale method at baseline,6months and 12months. For the families,only home blood pressure was measured at each visit.Results:1) In indicated cases,mean systolic blood pressure were significantly lower in the salt substitute group compared to the regular salt group at the months 3,6 and 12 no matter in office or at home(all P＜0.05).The systolic blood pressure in office decreased -9.5%vs-6.5%,-7.5%vs-5.1%,-10.7%vs-8.0%and the systolic blood pressure at home decreased 4.5%vs-1.8%,-0.9%vs1.0%,-4.8%vs-2.2%in the salt substitute and the regular salt group at the months 3,6 and 12,respectively.The control rate of hypertension significantly increased at months 3 and persisted throughout the trial in the mineral group compared with controls.During intervention period,the net changes were 5.3(95%CI:1.0-9.5)mmHg,4.2(95%CI:1.3-7.0)mmHg and 2.9(95%CI:-0.3～6.1)mmHg by OBPM,HBPM and ABPM respectively.Further analysis showed that body weight did not change during the study period in both groups,but the frequencies of anti-hypertensive medication using dropped faster than control group and significantly different between the 2 groups(p＜0.05).In the patient with same treatment and without treatment at each visit,significant antihypertensive effects of substitute salt were found.2) In the hypertensive patients of families,the systolic blood pressure in office decreased -7.5%vs-6.3%,-4.2%vs-1.7%,-6.0%vs-3.1%in the salt substitute and the regular salt group at the months 3,6 and 12,respectively(all p＜0.05).The net changes was 6.5(95%CI:1.8-11.2) mmHg.In the non-hypertensive patients of families,the systolic blood pressure in office changed -0.8%vs0.1%,2.8%vs3.2%,-0.4%vs-0.3%in the salt substitute and the regular salt group at the months 3,6 and 12,respectively(all p＞0.05). The net change was 0.2(95%CI:-2.5～2.1)mmHg.3) The magnitudes of diastolic blood pressure decrease were greater in the salt substitute group than in the regular salt group, although there were no detectable differences between groups for diastolic blood pressure at any time point in office or at home(all P＞0.05).4) 97%of hypertensive patients and 83%families completed the study.One hundred percent of participants in intervention group wholly or almost wholly used our provided salt(salt substitute) and 98%in control group used our provided salt(regular salt).The compliance differed not between two groups(p＞0.05).The concentrations of urine potassium significantly increased in salt substitute group after intervention and were higher than in the regular salt group.The net changes of urine potassium were 7.6(95%CI:0.8～14.4) mmol/L.The ratio of urine sodium and urine potassium was significantly lower in the salt substitute group than in the regular salt group after intervention.The net changes of urine sodium and the ration of urine sodium to potassium were 8.0(95%CI:-9.6～25.7) mmol/L and 1.1(95%CI: 0.2～2.0) respectively.5) The markers of renal function including creatinine and urea nitrogen and the concentration of serum sodium and potassium not significantly changed before and after intervention,and there were no significantly differences between two groups.6) The scores of taste(including saltiness and like) were similar between the two groups during intervention.Conclusion:replacing regular salt by a low sodium,high potassium salt could offer a valuable non-pharmacological approach to lowering systolic blood pressure by office or home blood pressure measurement in Chinese,and it was safe and feasible and good acceptability during long-term.