Relations Of Overnight Urinary Sodium And Potassium With The Risk Of Cardiovascular Disease

ObjectiveTo explore the relation of overnight urinary sodium,potassium,and sodium to potassium ratio with the risk of cardiovascular disease(CVD).MethodsThe People's Republic of China-United States Collaborative Study of Cardiovascular and Cardiopulmonary Epidemiology(PRC-USA collaborative study)was carried out in the autumn of 1983-1984 in 4 population samples from northern and southern in China,and participants were surveyed for cardiovascular risk factors.A subsample of 10 percent of the participants(3 5?59 years old)was randomly selected and collected for three consecutive days overnight urine samples and 24-hour dietary data at the first survey in the autumn of 1983-1984 and the repeated survey in the spring of 1985-1986.Dietary nutrient intake level were detected,and urinary sodium and potassium were detected and calculated for 8 hours excretion,and the mean of 6 days overnight urinary sodium and potassium in two seasons were used.Participants were followed-up from 1987-1988 until the end of 2005 with the interval of 2 years.The occurrences of cardiovascular events were recorded.Participants were divided into three groups according to the tertiles of overnight urinary sodium,potassium and sodium to potassium ratio,respectively.Comparing the incidence of cardiovascular events(including stroke and coronary heart disease)in each group.Cox proportional hazard regression model was used to determine the relationship between urinary sodium,potassium and sodium to potassium ratio and the risk of CVD.In addition,participants were divided into 2 groups by the median of urinary sodium and urinary potassium,and then combined each other for 4 groups including high sodium-low potassium group,high sodium-high potassium group,low sodium-low potassium group,and low sodium-high potassium group.The high sodium-low potassium group was regarded as the reference,to explore the relationship between different sodium-potassium combinations and the risk of CVD.ResultsA total of 954 participants were included in the final analysis,the mean age was(46.44±6.20)years,of whom 459(48.11%)were males,411(43.08%)were northern population,491(51.47%)lived in the urban.After a median follow-up of 18.6(18.3,19.3)years,cardiovascular events occurred in 81(8.49%)participants,including 64 stroke and 20 coronary heart disease events.The incidence of cardiovascular events in urinary sodium tertiles was 3.77%,7.23%and 14.47%,respectively.Multivariate regression analysis after adjusted for age,sex,urban or rural,type of work,smoking,alcohol consumption,total cholesterol,body mass index,north or south,educational levels,total energy intake,urinary potassium,systolic blood pressure and taking antihypertensive drugs,there was an increasing trend of CVD risk by the rising of sodium excretion levels(P for trend=0.002).As compared with the first group,the hazard ratios(HRs)and 95%confidence intervals(CIs)in the second and the third sodium groups were 1.80(0.85-3.81)and 3.35(1.50-7.50).The incidence in three urinary sodium to potassium ratio tertiles was 4.09%,10.06%and 11.32%,respectively(P for trend=0.0005).Multivariate analysis showed that when compared with the first tertile group,the CVD risks in the second and third ratio group were increased for 1.11-fold(HR,2.11;95%CI,1.09?4.08)and 1.13-fold(HR,2.13;95%CI,1.09?4.15),respectively.The incidence of CVD in three urinary potassium groups was 5.03%,9.12%and 11.32%,respectively(P for trend=0.002).When adjusted for confounding factors in the model,there was no significant association between urinary potassium and CVD.As compared with the first tertile group,the HR and 95%CI in the second and third urinary potassium groups were 1.52(0.80-2.90)and 1.30(0.63-2.69).In addition,using the high sodium-low potassium group as reference,the CVD risk in high sodium-high potassium group did not reduce(HR,1.04;95%CI,0.56-1.95),The risk in low sodium-low potassium group has reduced by 61%(HR,0.39;95%CI,0.18-0.85).And the risk in low sodium-high potassium group was the lowest,the CVD risk has reduced for 68%(HR,0.32;95%CI,0.11?0.93)when compared with the reference.ConclusionsOvernight urinary sodium,urinary sodium to potassium ratio were both positively associated with the risk of cardiovascular events.In high sodium level,the risk of CVD may not be decreased even if urinary potassium was high.In low sodium level,regardless of the urinary potassium level,the CVD risks were decreased significantly.It is concluded that prevention of cardiovascular disease should change the high sodium-low potassium dietary pattern,increasing the intake of potassium,but we should pay more attention to reducing sodium intake.