The Associations Of Time-averaged Serum Uric Acid With Cardiovascular Mortality And All-cause Mortality In Peritoneal Dialysis Patients

Objective:To investigate the effect of time-averaged serum uric acid（TA-SUA）on cardiovascular mortality and all-cause mortality in peritoneal dialysis（PD）patients.Methods:A retrospective cohort study was designed.The patients on stable continuous ambulatory peritoneal dialysis（CAPD）treatment for more than 3 months were enrolled from the PD Center of Peritoneal Dialysis Center of General Hospital of Ningxia Medical University Hospital during the January 1^st,2007 to the December 31^st,2007.The information of baseline demographic characteristics,laboratory test items and the follow-up data were collected.The TA-SUA was calculated by the area under the curve of serum uric acid change during the follow-up period.The subjects were divided into four groups according to their TA-SUA level quantiles（Q1:<5.1mg/dL,Q2:5.1-5.8mg/dL,Q3:5.8-6.8mg/dL,Q4>6.8mg/dL）.The clinical characteristics to compared between the four groups.Kaplan-Meier method and Cox regression model were used to analyze the relationship between TA-SUA and cardiovascular mortality as well as the all-cause mortality.Results:（1）A total of 487 CAPD patients were enrolled in this study,including 232 cases of male（47.6%）and 255 cases of female（52.4%）.The average age was（51.8±14.4）years.The median follow-up time was 29.5 months and the longest follow-up time was 120.6 months.（2）The average TA-SUA of all participants was 6.09±1.70mg/dL.The comparson of the baseline clinical characteristics in the four groups showed that the Q1 group was elder with lower body mass index,lower diastolic blood pressure,less ultrafiltration volume.There were more diabetes,malnutritional patients in the Q1 group.The level of serum potassium,serum urea nitrogen,serum creatinine,baseline serum uric acid were significantly lower,while the high density lipoprotein and the low density lipoprotein levels were higher in the Q1 group than all the other groups（p<0.05）.（3）At the end of follow-up,a total of 197（40.5%）cases died.The primary cause of death was cardiovascular diseases（CVD）death in 109（55.3%）cases.（4）The Kaplan-Meier analysis showed that the all-cause mortality was significantly higher in Q1 group versus Q2group（log rank=5.065,p=0.024;Breslow=5.567,p=0.016）,Q1 group versus Q3 group（log rank=17.348,p<0.001;Breslow=17.569,p<0.001）,Q1groupversusQ4group（log rank=24.373,p<0.001;Breslow=22.952,p<0.001）,Q2groupversusQ3group（log rank=9.012,p=0.003;Breslow=7.495,p=0.006）.Thesimilarresultswasfoundinthe cardiovascular survival analysis.There was no significant difference in both all cause mortality and cardiovascular mortality between the Q2 and Q3,Q2 and Q4,Q3 and Q4（p>0.05）.（5）COX regression model analysis showed that after adjustment for the traditional cardiovascular risk factors and uremia related risk factors,the decreased TA-SUA level was an independent risk factor for all-cause mortality in PD patients.Each 1 mg/dL decreasing of TA-SUA level was associated with 23%increasing of all-cause mortality（HR=0.773,95%CI（0.62-0.97）,p=0.027）.Conclusion:PD patients with low TA-SUA were older and had a higher proportion of diabetes and malnutritions than those with higher TA-SUA;A lower TA-SUA levels was an independent risk factors for all-cause mortality in PD patients.