Abstract
Objective: To compare overall survival and technical survival in diabetic mellitus (DM) and non-DM (N-DM) Chinese patients undergoing peritoneal dialysis (PD), and to discuss the factors involved. Methods: Clinical data were analyzed for all adult patients (age >18 years) with chronic renal failure who had commenced PD between 2006 and 2010 in a single Chinese center. Results: Compared to the N-DM group, the DM group was older (64.5 ± 11.9 years vs. 59.2 ± 15.2 years, p = 0.023), with a higher body mass index (BMI) (25.2 ± 3.5 kg/m2 vs. 23.2 ± 3.5 kg/m2, p = 0.001), a higher estimated glomerular filtration rate (eGFR) (10.4 ± 4.7 mL/min/1.73 m2 vs. 6.9 ± 2.9 mL/min/1.73 m2, p = 0.000), and lower intact parathyroid levels (81.35 pg/mL vs. 186.3 pg/mL, p = 0.003). During the average 23.8-month follow-up period, the 1-, 2-, and 3-year survival rates of the DM group were 95.8%, 69.2%, and 60%, respectively. The 1-, 2-, and 3-year survival rates of the N-DM group were 87.2%, 76.5%, and 66.7%, respectively. There was no significant difference in survival between the groups. The 1-, 2-, and 3-year technical survival rates of the DM group were 93.8%, 69.2% and 60%, respectively. The 1-, 2-, and 3-year technical survival rates of the N-DM group were 84.6%, 72.5% and 63.3%, respectively. There was no significant difference in technical survival between the groups. Within the DM group, the only factor predictive for both overall survival (p = 0.015) and technical survival (p = 0.009) was the initial BMI, and both survival outcomes in DM patients with a BMI greater than 24 were higher than those observed with a BMI less than 24. Conclusions: In the first 3 years of PD, DM and N-DM patients have similar survival rates. Chinese DM patients with a higher BMI undergoing PD appear to have higher survival rates than those with a lower BMI.
INTRODUCTION
With a rapid rise in the prevalence of diabetes mellitus (DM) in China, the number of patients with end-stage renal disease (ESRD) due to diabetic nephropathy (DN) continues to increase. Increasing numbers of patients with ESRD caused by DN are involved in peritoneal dialysis (PD) programs as a result of cardiovascular disease and the problem of establishing access for hemodialysis. Therefore, an increasing number of patients with DN are undergoing PD. In order to learn more about survival rates and the factors that impact these in diabetic and non-diabetic patients, we analyzed data from new PD patients at our hospital.
PATIENTS AND METHODS
Patients
We selected adult (age ≥18 years) patients who started continuous ambulatory peritoneal dialysis (CAPD) in Peking University People’s Hospital between January 2006 and December 2010. Exclusion criteria included (1) patients undergoing dialysis as a result of acute renal failure, (2) patients with limited life expectancy due to the presence of cancer or other serious organ disease, and (3) patients transferred from undergoing hemodialysis or renal transplantation. Patients were divided into two groups: the DM group and the non-DM (N-DM) group.
Methods
We collected the initial clinical data, including gender, age, previous history of cardiovascular disease (CVD), body mass index (BMI), blood pressure, hemoglobin, estimated glomerular filtration rate (eGFR), and levels of serum albumin, uric acid, calcium, phosphate, intact parathyroid hormone (iPTH), lipids, and electrolytes. Patients were followed up regularly, at least once every 3 months, and blood pressure, episodes of peritonitis, residual renal function, the adequacy of dialysis (KT/V/w, Ccr/w), and levels of hemoglobin, albumin, uric acid, calcium, phosphate, lipids, and electrolytes were all determined at these time points. Follow-up ended in June 2011. End points included death, renal transplantation, and transfer to hemodialysis. All events and etiological factors were recorded.
Statistical Analyses
All analyses and calculations were performed using the SPSS statistical package, version 17.0 (SPSS, Chicago, IL, USA). Data normally distributed are presented as mean ± standard deviation (SD). Comparisons of measurement data between the two groups were performed using independent student’s t-tests. Data with a non-normal distribution are presented as median, and comparisons between two groups were conducted using rank sum test. Comparisons of enumeration data between two groups were undertaken using the chi-square test. Differences in survival rates between groups were obtained with Kaplan–-Meier survival analysis and the log-rank test. Factors that influenced survival were analyzed using Cox multifactor regression (gradual backward method).
RESULTS
On Commencing PD
The study consisted of 142 patients, with 56 (39.4%) in the DM group and 86 (60.4%) in the N-DM group. Compared to the N-DM group, patients in the DM group were older at the initiation of dialysis (64.5 ± 11.9 years vs. 59.2 ± 15.2 years, p = 0.023), had a higher BMI (25.2 ± 3.5 kg/m2 vs. 23.2 ± 3.5 kg/m2, p = 0.001), a higher eGFR (10.4 ± 4.7 mL/min/1.73 m2 vs. 6.9 ± 2.9 mL/min/1.73 m2, p = 0.000), and lower iPTH levels (81.35 pg/mL vs. 186.3 pg/mL, p = 0.003). There was a tendency toward a higher prevalence of CVD in the DM group, although the difference was not statistically significant (35.7% vs. 20.9%, p = 0.052). There were no significant differences in blood pressure or levels of hemoglobin, albumin, uric acid, lipids, and electrolytes between the two groups ().
Table 1. Comparison of general features between DM and N-DM groups at commencement of peritoneal dialysis.
Comparison of Outcomes between the DM and the N-DM Groups
Across the entire study population, the mean follow-up period was 23.8 ± 14.4 months, the DM group with 22.9 ± 13.4 months, and the N-DM group with 24.5 ± 15.1 months. There was no significant difference between the groups. During the follow-up period, three patients underwent renal transplantation (one in the DM group, two in the N-DM group); four patients were transferred to hemodialysis (one in the DM group, three in the N-DM group); and 30 patients died (13 in the DM group, 17 in the N-DM group). The leading cause of death in the DM group was cardiovascular disease (6/13, 46.2%), followed by cerebrovascular disease (2/13, 15.4%), tumor (2/ 13, 15.4%), and infection (1/13, 7.7%). In the N-DM group, the leading cause of death was also cardiovascular disease (5/17, 29.4%), followed by cerebrovascular disease (3/17, 17.6%), infection (3/17, 17.6%), and tumor (2/17, 11.8%). There were no significant differences in causes of death between the two groups.
Comparison of Survival Rates between the DM and the N-DM Groups
The 1-, 2,- and 3-year survival rates in the DM group were 95.8%, 69.2%, and 60% and in the N-DM group, 87.2%, 76.5%, and 66.7%, respectively. There were no significant differences in survival rates between the two groups. Kaplan–-Meier survival analysis showed that, although after 2 years of treatment, the DM group demonstrated a tendency towardlower survival rates; there was no significant difference in cumulative survival rates when compared with the N-DM group (p = 0.489, ).
Figure 1. Comparison of cumulative survival rates between DM and N-DM patients on PD.
Comparison of Technical Survival Rates between the DM and the N-DM Groups
The 1-, 2-, and 3-year technical survival rates in the DM group were 93.8%, 69.2%, and 60% and in the N-DM group, 84.6%, 72.5%, and 63.3%, respectively. There were no significant differences in technical survival rates between the two groups. In addition, Kaplan–-Meier survival analysis showed no significant differences in overall technical survival rates between the two groups (p = 0.652, ).
Figure 2. Comparison of cumulative technical survival rates between DM and N-DM patients on PD.
Factors Influencing Survival in the DM Group
Sex, age, a history of cardiovascular or cerebrovascular disease, BMI, baseline eGFR, serum albumin, calcium, phosphate, and uric acid at commencement of PD, time-averaged serum albumin, calcium, phosphate, uric acid, KT/V urea, Ccr/w during the follow-up period and episodes of peritonitiswere all included in the Cox model regression analysis. Results revealed that BMI was the only factor significantly associated with survival (p = 0.015).
Dividing DM patients into two groups according to the BMI demonstrates that a BMI value >24 was associated with a higher survival rate than a value <24 (p = 0.014, ).
Figure 3. Impact of BMI on survival in patients with DM.
Figure 4. Impact of BMI on technical survival in patients with DM.
Factors Influencing Technical Survival in the DM Group
Sex, age, a history of cardiovascular or cerebrovascular disease, BMI, baseline eGFR, serum albumin, calcium, phosphate and uric acid at commencement of PD, time-averaged serum albumin, calcium, phosphate, uric acid, KT/V urea, Ccr/w during the follow-up period, and episodes of peritonitis were all included in the Cox model regression analysis. Results revealed that BMI was the only significant factor associated with technical survival (p = 0.009).
Dividing DM patients into two groups according to the BMI demonstrates that a BMI value >24 was associated with a higher technical survival rate than a value <24 (p = 0.014, ).
DISCUSSION
According to a 2007–2008 epidemiological survey, 9.7% of adults (age >20 years) in China have diabetes, which makes China the country with the greatest prevalence of diabetes worldwide.Citation1 As a result of this high prevalence rate, an increasing number of patients are developing DN and ESRD. Among patients undergoing PD in our hospital, DN has become the primary etiological factor, accounting for 39.4%, which is close to the figure reported by the 2010 annual data report of US Renal Data System (USRDS).Citation2
However, whether or not the patients with DN are appropriate for PD remains controversial. Glucose in peritoneal dialysate increases glucose uptake, which can exacerbate insulin resistance. In addition, protein loss from the effluent fluid may increase malnutrition.
Data from USRDS 2010 revealed that the overall 1-, 2-, and 3-year survival rates for patients on PD were 83%, 67.2%, and 53.8%, respectively, whereas those for a DM subgroup were 80.3%, 61.7%, and 46.6%, respectively.Citation2 A further study from the Toronto Western Hospital, Canada showed that the 1-, 2-, 3-, and 5-year survival rates were 91%, 76%, 66%, and 47%, respectively, in diabetics, and 94%, 89%, 84%, and 69%, respectively, in non-diabetics.Citation3 Data from single centers in Asia and Europe also showed that survival rates were significantly lower in diabetic than in non-diabetic PD patients.Citation4 However, our study found that even though patients with DM were older and had a higher incidence of CVD (p = 0.052), there were no significant differences in the 1-, 2-, and 3-year survival rates. Further analysis found that the DM group had a higher baseline eGFR than the N-DM group. The CANUSA study reported that residual renal creatinine clearance was the important factor predictive of prognosis in patients undergoing PD.Citation5 Therefore, we presume that the similar survival rates in the DM and the N-DM groups observed in our center may be explained by the presence of a better residual renal function at the commencement of dialysis. However, as we all know, DM patients are usually recommended to start dialysis earlier than N-DM patients. So, the similar survival rates may involve some other factors such as intensive patient education, more frequent follow-ups, and paying more attention to DM patients.
Sipahioglu et al. conducted a retrospective study of 423 patients on PD in a single Turkish center and discovered that an older age at commencement, transfer from hemodialysis, and a history of CVD were independent risk factors for increased mortality.Citation6 Fang reviewed 358 patients on PD in the Toronto Western Hospital and found that advancing age was the only independent factor predictive of death in patients with DM. Our study found that BMI was the only significant factor associated with survival in those with DM on PD, with a higher BMI associated with an enhanced survival rate. This is similar to the “reverse epidemiology” found in hemodialysis patients. Contrary to the fact that in the general population those with higher BMIs and those who are obese are at a higher risk of cardiovascular disease and all-cause mortality, patients on hemodialysis who are overweight and obese may actually experience a survival benefit.Citation7 Theoretically, therefore, patients on PD may also demonstrate similar “reverse epidemiology”. Mutsert analyzed 689 patients on PD in the NECOSAD cohort data and found that, when comparing those with a BMI between 18.5 and 25 to those with a BMI > 30, there was no increase in mortality in the overweight and the obese. However, there was a two-fold increase in mortality in those with lower BMIs (BMI < 18.5).Citation8 We assume that a higher BMI is associated with enhanced survival as a result of better nutrition and greater energy reserves.
The study of technical survival by Prowant found that rates were lower in patients on PD with a BMI > 25.Citation9 They interpreted this result as a reflection of the fact that patients with a high BMI have a larger body surface area and a poorer dialysis adequacy (particularly less clearance of small molecular solutes). As a result, the technical survival rate is lower and more of these patients stop PD. In contrast, Chinese patients with DM and a higher BMI in our study had greater technical survival rates. It is possible that the range and average of BMI values in our patients were lower than those generally observed in Europeans and Americans.
However, the study has several limitations which cannot be avoided. First, it is a single center study, and the patients might have been chosen with bias. Second, the study involved only 142 patients and compared the first 3 years survival rates. The sample size may not be large enough, and duration may not be long enough to show the differences between the two groups.
CONCLUSIONS
In the first 3 years of PD, survival in the DM group was similar to that of the N-DM group due to intensive follow-ups. In Chinese patients with DM on PD, those with a higher BMI had higher overall survival and technical survival rates than those with a lower BMI. The results of this study demonstrate that patients with DM are appropriate for PD.
Declaration of interest
The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.
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- United States Renal Data System. 2010 USRDS Annual Data Report: Atlas of Chronic Kidney Disease and End-Stage Renal Disease in the United States. Bethesda, MD: National Institute of Diabetes and Digestive and Kidney Diseases; 2010.
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