Relationship Between Salt Intake And Earlier Renal Damage In Hypertensive Patients

BACKGROUND AND OBJECTIVEWith the development of world economy and industrialization, there is a sharp increasein the population of hypertension. However, the rates of awareness, treatment and control inChinese patients with essential hypertension are far below the level of developed countries.Because of the harm of hypertension on cardiovascular and other target organs, it not onlyaffects patients’ life and health greatly and brings economic burden to society, but alsoinfluences our social development greatly. How to prevent the onset of hypertensioneffectively and control hypertension and its complications has always been the hot spot ofthe clinical research.The pathogenesis of essential hypertension is complicated，of which unhealthy livinghabits are the major causes of hypertension and its complications. Epidemiological studiesshow that average blood pressure and sodium intake were positively correlated. Highsodium intake can not only induce the rise in blood pressure by increasing the renal andcardiovascular load, but also directly damage the kidneys and cardiovascular tissues, whichresults in the deterioration of kidney and cardiovascular system. Currently, sodium has beenconsidered as a risk factor for cardiovascular disease. Sodium intake is closely related to thepathogenesis and development of hypertension. In the case of steady diet, the dailyexcretion of urinary sodium and the daily intake of dietary sodium are equal.24-hour (24h)urinary sodium excretion, which is a more accurate and reliable method, is often used toassess the intake of the individual daily salt in studies.It has been proved that intervention of unhealthy lifestyles can effectively slow downthe occurrence of hypertension and its target organ damage. Therefore, it is significant toraise our awareness of the relationship between salt intake and target organ in thepathogenesis, pathology, perniciousness and other relevant aspects. It is extremelyimportant to promote early health education and limit sodium intake for controlling blood pressure and preventing cardiovascular events. Therefore, we tested24h urinary sodiumexcretion to reflect the individual daily salt intake in this study. Moreover, we investigatedthe relationship between salt intake and early kidney damage in the hypertensive patients,so as to elucidate the importance of salt intake control in hypertension and earlier kidneydamage.OBJECTIVEWe collected418hospitalized patients with essential hypertension, including195males and223females, aged between18and79years, in Daping Hospital affiliated to theThird Military Medical University from November2011to October2013.Hypertension was defined as systolic blood pressure (SBP)≥140mmHg and/ordiastolic blood pressure (DBP)≥90mmHg or as current use of antihypertensive medicationaccording to " Chinese Guidelines for Prevention and Control of Hypertension (2010)".All the subjects were divided into four groups according to the quartiles of the saltintake, namely the low salt group (salt intake≤6.8g/d), medium salt group (6.8g/d <saltintake≤9.9g/d), middle to high salt group (9.9g/d <salt intake≤13.7g/d) and high saltgroup (salt intake>13.7g/d).Daily salt intake should not exceed6g based on " Chinese Guidelines for Preventionand Control of Hypertension (2010)". The418cases were divided into standard group (saltintake≤6g/d) and superscalar group (salt intake>6g/d). And then the two groups werefurtherly divided into abdominal obesity and non-abdominal obesity group. Abdominalobesity was diagnosed according to "Chinese Experts Consensus for Prevention andControl of Adult Obesity (2011)", namely waist circumference (WC)≥85cm for women,waist circumference≥90cm for men.METHODSAll patients were inquired about their history of hypertension, smoking and drinkingand then detected the following parameters, including serum sodium, serum potassium,serum chlorine, fasting plasma glucose, serum creatinine, uric acid, blood urea nitrogen,cystatin C, total cholesterol, triglyceride, high-density lipoprotein cholesterol, low-densitylipoprotein cholesterol. The height, body weight, WC, body mass index (BMI), SBP andDBP were measured by an independent physician.24h urinary sodium, potassium, chlorine, microalbumin and urine volume were recorded after24h urine was collected. Thedifferences of microalbuminuria and index of body fat between four groups were analysed.One-way ANOVA was performed to analyse the general clinical data, serum markers,24hurinary sodium and microalbumin. Multiple linear regression was performed to analysewhich were the independent risk factors of the increased24h urinary microalbumin. P<0.05was regarded as statistically significant. All statistical tests were performed usingSPSS17.0.RESULT1. The salt intake of male hypertensive patients was significantly higher than that offemale (P=0.002).2. The rate of early renal damage in the four groups was significant different (P=0.001). With unadjusted synergistic factors,24h urinary microalbumin increasedsignificantly with salt intake (P <0.01), and this trend still existed after adjustment of bloodpressure and other confounding factors. After all variables were adjusted, the mean urinarymicroalbumin in the high salt group was significantly higher than that in the low salt groupand medium salt group (P <0.001; P=0.004). Meanwhile the mean urinary microalbumin inthe middle to high salt group was higher than that in the low salt group (P=0.003). Multiplelinear regression analysis showed that salt intake, DBP, and FBG were independent riskfactors for urinary microalbumin in hypertensive patients.3. Both patients were taken the salt content in high or low level, the24h urinarymicroalbumin in the patients with abdominal obesity were higher than that innon-abdominal obesity (P <0.05), an average increase of about23%. The24h urinarymicroalbumin in the superscalar group in the patients with abdominal obesity was highercompared with that of non-abdominal obesity and the standard group with abdominalobesity (P <0.05).24h urinary microalbumin was positively correlated with body weight(r=0.103, P=0.035), WC(r=0.133, P=0.007), BMI (r=0.129, P=0.008).4. Body weight (P <0.001), WC (P=0.001) and BMI (P=0.01) in the four groups wassignificant different. Body weight and WC in the high salt group were significantly highercompared with those in the low salt group, medium salt group and middle to high salt group(P <0.05). BMI in the high salt group was significantly higher compared with that in the low salt group and medium salt group (P <0.05). Salt intake was positively correlated withWC(r=0.212, P <0.001), BMI (r=0.177, P <0.001).CONCLUSIONLong-term high-salt diet is an independent risk factor for early renal damage inhypertensive patients. The more the daily intake of salt, the higher the incidence of earlyrenal damage and the more serious degree of renal damage. Salt intake was positivelycorrelated with WC and BMI. Abdominal obesity increases the risk of high-salt diet onearly renal damage in hypertensive patients.