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Part 4: Metabolic Syndrome and Nutrition in PD |
Departments of Nephrology and of Dietetics,1 Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India
Correspondence to: N. Prasad, Department of Nephrology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow 226014 India. narayan{at}sgpgi.ac.in
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ABSTRACT |
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 TOP ABSTRACT PATIENTS AND METHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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Background: Case-mix comorbidities and malnutrition
influence outcome in continuous ambulatory peritoneal dialysis (CAPD)
patients. In the present study, we analyzed the influence of stratified
comorbidities on nutrition indices and survival in CAPD patients. Patients and Methods: We categorized 373 CAPD patients
(197 with and 176 without diabetes) into three risk groups: low—age
under 70 years and no comorbid illness; medium— age 70 – 80 years,
or any age with 1 comorbid illness, or age under 70 years with diabetes;
high—age over 80 years, or any age with 2 comorbid illnesses. We then
compared nutrition indices and malnutrition by subjective global assessment
(SGA) between the three groups. Survival was compared using Kaplan–Meier
survival analysis. Results: Mean daily calorie and protein intakes in the
low-risk group (21 ± 6.7 Kcal/kg, 0.85 ± 0.28 g/kg) were
significantly higher than in the medium- (17.6 ± 5.2 Kcal/kg, 0.79
± 0.25 g/kg) and high-risk (17.5 ± 6.1 Kcal/kg, 0.78 ±
0.26 g/kg) groups (p = 0.001 and p = 0.04 respectively).
Relative risk (RR) of malnutrition was less in the low-risk group (103/147,
70.06%) than in the medium-risk group [135/162, 83.3%; RR: 2.0; 95% confidence
interval (CI): 2.1 to 3.4; p = 0.01] or the high-risk group (54/64,
84.4%; RR: 2.3; 95% CI: 2.1 to 4.9; p = 0.03). Mean survivals of
patients in the low-, medium-, and high-risk groups were 51
patient–months (95% CI: 45.6 to 56.4 patient–months), 43.3
patient–months (95% CI: 37.8 to 48.7 patient–months), and 29.7
patient–months (95% CI: 23 to 36.4 patient–months) respectively
(log-rank: 35.9 patient–months; p = 0.001). The 1-, 2-, 3-, 4-,
and 5-year patient survivals in the low-, medium-, and high-risk groups were
96%, 87%, 79%, 65%, and 56%; 89%, 67%, 54%, 43%, and 34%; and 76%, 48%, 31%,
30%, and 30% respectively. Conclusions: Intake of calories and protein was
significantly lower in the medium-risk and high-risk groups than in the
low-risk group. Survival was significantly better in low-risk patients than in
medium- and high-risk patients.
KEY WORDS: Comorbidities; stratification; survival.
Treatment of patients with end-stage renal disease (ESRD) aims to prolong life and achieve good nutrition status and the greatest possible well-being and function. Several factors predict mortality in ESRD patients on continuous ambulatory peritoneal dialysis (CAPD). Comorbidity is an inevitable prognostic factor, and case-mix comorbidity has a profound influence on outcome in CAPD patients (1,2). Several studies have reported on the quantification and adjustment of comorbidities related to survival in CAPD patients (3–5). Malnutrition is another problem associated with comorbidities in CAPD patients (6,7). The combined presence of comorbid disease and malnutrition further increases mortality (8).
The mean age of our CAPD patients is lower than that of CAPD patients in Western countries (9), and most of our CAPD patients are malnourished at CAPD initiation (10). Comorbidities may also be different in Indian CAPD patients. It has been observed that patients with comorbidities have a more stringent and restricted diet. Nutrient intake and risk of malnutrition may be different in different risk groups stratified by comorbidities. There is a paucity of data on survival and stratified comorbidities from India, where PD has been established as a modality of renal replacement therapy for about two decades. There is also a paucity of data on nutrition indices in CAPD patients stratified by comorbidities. We undertook the present study to analyze the influence of comorbidities on nutrient intake, various indices of nutrition, and survival in CAPD patients.
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PATIENTS AND METHODS |
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TOPABSTRACTPATIENTS AND METHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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Nutrition was assessed for all patients by anthropometry, 72-hour dietary diary, body mass index (BMI), serum albumin, and subjective global assessment (SGA— a validated estimate of nutrition status for patients treated with peritoneal dialysis). The SGA was assessed using the dialysis malnutrition scoring system proposed by Kalantar–Zadeh et al. (11). We calculated BMI using the standard formula: weight divided by the square of height in meters. These parameters were assessed at 4 – 6 weeks, 6 months, and 12 months after initiation of CAPD. The means of these values for all parameters of nutrition were considered the final values for the comparisons between the three risk groups. We then compared nutrient intake and nutrition status between the risk groups. We also compared patient survival in the risk groups.
All-cause and cardiovascular death were the outcomes of interest. Cardiovascular death was defined as death attributable to myocardial infarction, atherosclerotic heart disease, cardiomyopathy, arrhythmia, valvular heart disease, cerebrovascular disease, mesenteric infarction, and peripheral vascular disease. The endpoints of the study were patient death, transplantation, transfer to hemodialysis, or the end of the study period.
STATISTICAL ANALYSIS
Actuarial survival rates were determined by the Kaplan–Meier method.
A log-rank test was used to compare patient survival between the groups.
All-cause mortality was considered an event during the survival analysis. The
patients who received renal grafts and who were shifted to maintenance
hemodialysis were censored during the survival analysis. The Student
t-test or the Kruskal–Wallis test was used to compare
differences in clinical characteristics between the groups. The chisquare test
was used to compare proportions between groups. Data are presented as mean
± standard deviation. A difference was considered significant when the
p value was less than 0.05. All data were analyzed using the SPSS
statistical software package (version 10: SPSS, Chicago, IL, U.S.A.).
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RESULTS |
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TOPABSTRACTPATIENTS AND METHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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On stratification by comorbidities, 147 patients were classified as low risk; 162, as medium risk; and 64, as high risk. The mean age of the patients in the low-risk group (43.95 ± 14.29 years) was significantly less than that in the medium- and high-risk groups (56.76 ± 10.83 years, p = 0.001, and 55.32 ± 11.41 years, p = 0.001, respectively). The proportion of men (men:women) in the medium-risk (132:30) and high-risk (54:10) groups was higher than that in the low-risk group (83:64).
NUTRIENT INTAKE AND NUTRITION STATUS
On analyzing nutrient intakes, the mean daily calorie intakes in the
medium-risk (17.6 ± 5.2 Kcal/kg, p = 0.006) and high-risk
(17.5 ± 6.1 Kcal/kg, p = 0.003) groups were significantly
lower than the intake in the low-risk group (21 ± 6.7 Kcal/kg).
However, daily calorie intake was similar in the medium- and high-risk groups.
In all three risk groups, daily calorie intakes were significantly lower than
the intake recommended by the U.S. National Kidney Foundation's Kidney Disease
Outcomes Quality Initiative (NKF-K/DOQI) guideline for CAPD patients (35
Kcal/kg).
The daily protein intakes in patients in the medium-risk (0.79 ± 0.25 g/kg, p = 0.04) and high-risk (0.78 ± 0.26 g/kg, p = 0.04) groups were also significantly lower than the intake seen in patients in the low-risk group (0.85 ± 0.29 g/kg). In all study groups, daily protein intake was also significantly lower than the protein intake recommended by the NKF-K/DOQI guideline for CAPD patients.
On SGA, the number of patients with a normal nutrition status was significantly higher in the low-risk group (n = 44, 29.93%; p = 0.027) as compared with the medium-risk (n = 27, 16.88%) and high-risk (n = 10, 15.63%) groups. The proportion of patients with a normal nutrition status was similar in both the medium-risk (16.88%) and the high-risk (15.63%) groups. The number of patients with a mild-to-moderate grade of malnutrition was significantly higher in the low-risk group (n = 95, 64.63%) than in the medium-risk group (n = 117, 72.22%) or the high-risk group (n = 46, 71.88%). The proportion of patients with a severe grade of malnutrition was significantly higher in the medium-risk (n = 18, 11.25%) and high-risk (n = 8, 12.5%) groups than in the low-risk group (n = 8, 5.44%). The relative risk (RR) of malnutrition was significantly higher in the medium-risk [135/162, 83.3%; RR: 2.45; 95% confidence interval (CI): 1.38 to 4.36.4; p = 0.002] and high-risk (54/64, 84.4%; RR: 2.49; 95% CI: 1.1 to 5.27; p = 0.019) groups than in the low-risk (103/147, 70.06%) group.
Mean serum albumin levels were significantly higher in the low-risk group (3.34 ± 0.57 g/dL) than in the medium-risk (3.16 ± 0.53 g/dL, p = 0.006) and high-risk (3.16 ± 0.61 g/dL, p = 0.04) groups. The proportion of patients with a serum albumin level below 3 g/dL was significantly higher in the medium-risk (55/162, 33.9%; p = 0.001) and high-risk (22/64, 34.4%; p = 0.01) groups than in the low-risk group (26/148, 17.6%). Based on serum albumin, the RR of developing malnutrition (serum albumin < 3 g/dL) was significantly lower in the low-risk group than in the medium-risk (RR: 2.39; 95% CI: 1.4 to 4.08; p = 0.001) and high-risk (RR: 2.44; 95% CI: 1.25 to 4.75; p = 0.001) groups.
PATIENT SURVIVAL AND STRATIFIED COMORBIDITIES
On Kaplan–Meier survival analysis, the mean survival of patients in
the low-risk group was 51 patient–months (95% CI: 45.6 to 56.4
patient–months); it was 43.3 patient–months (95% CI: 37.8 to 48.7
patient–months) in the medium-risk group and 29.7 patient–months
(95% CI: 23 to 36.4 patient–months) in the high-risk group (log-rank:
35.9 patient–months; p = 0.001). The 1-, 2-, 3-, 4-, and 5-year
patient survivals were, respectively, 96%, 87%, 79%, 65%, and 56% in the
low-risk group; 89%, 67%, 54%, 43%, and 34% in the medium-risk group; and 76%,
48%, 31%, 30%, and 30% in the high-risk group
(Figure 1).
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DISCUSSION |
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TOPABSTRACTPATIENTS AND METHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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The reason for the high incidence of malnutrition in the high-risk group could be the poor calorie and protein intakes seen in this group of patients as compared with patients in a low-risk group. The reason for poor nutrient intake in the medium- and high-risk groups is not clear, but could be a more stringent and restricted diet related to comorbidities. Although the calorie and protein intakes in all risk groups were also lower than the intakes recommended by NKF-K/DOQI, the energy and protein intakes were very low in the medium- and high-risk groups as compared with the low-risk group.
We recently studied changes in nutrition status in an incident cohort of our CAPD patients and showed that calorie and protein intakes remain lower than the intakes recommended by NKF-K/DOQI in most of our CAPD patients (10). The same study also showed that most of our CAPD patients are already malnourished at CAPD initiation (10). Wang et al. also observed overall poor nutrient intake in peritoneal dialysis patients as compared with age- and sex-matched controls (6). As in our study, the study by those authors noted a further decline in nutrient intake in patients with comorbidities. In a study on the effects of new comorbidities on nutrition status, Dong et al. showed that new comorbidities are associated with malnutrition in this group of patients (12). Chung et al. showed that malnutrition is an independent predictor of mortality and that the combined presence of comorbidities and malnutrition increases the mortality of PD patients (8). In the Chung study, the survival rate of CAPD patients in the medium- and high-risk groups was lower than that of patients in the low-risk group.
Davies et al. also observed notable separation of actuarial curves in three different risk groups (2). They noted that comorbidity has quantitative effect on mortality in peritoneal dialysis patients independent of age, residual renal function, and membrane function. In contrast to the Khan index (1) used in our study, the Davies index does not include age, because the index was specifically designed to be used in conjunction with age as an independent covariate. Other comorbidity indices that are in use in studies of ESRD patients—for example, the Khan (1) and Charlson (3) indices—assign various weights to various comorbidities, with the weights based on the effects of comorbid diseases on survival. It can be argued that the sheer number of comorbidities, as they appear in the commonly used Davies index (1), is a crude measure for the prognostic effects of comorbidities on health status. The poor survival of patients in a high-risk group was also observed with various indices in various studies. The 2-year survivals in the low-, medium-, and high-risk groups based on stratified comorbidities (Khan index) of the patients in the present study were 87%, 67%, and 48% respectively. The 2-year survivals in the low-, medium-, and high-risk groups (Khan index) of historical patients in the study by Khan et al. (1) was almost similar at 93%, 71%, and 56% respectively. And in studies by Davies et al. (2) and Hemmelgarn et al. (3), 2-year survivals in the low-, medium-, and high-risk groups were 91%, 66%, and 45% (Davies index), and 96%, 82%, and 54% (Charlson comorbidity index) respectively.
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CONCLUSIONS |
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