Confounding effect of comorbidities and malnutrition on survival of peritoneal dialysis patients

Abstract

Background and objectives: Malnutrition and comorbid diseases are strong predictors of mortality in patients on continuous ambulatory peritoneal dialysis (CAPD). We undertook this study to analyze the confounding impact of comorbidities and malnutrition on the survival of CAPD patients.

Methods: In this prospective, observational study, 342 CAPD patients (179 diabetics, 250 male, aged 51.5 ± 14 years) were followed for 21.62 ± 14.38 S.D. patient-months. Based on nutritional status and comorbidities, patients were categorized into four groups: (1), normal nutrition without comorbidities (n = 61, 17.8%); (2), normal nutrition with comorbidities (n = 26, 7.6%); (3), malnutrition with comorbidities (n = 160, 46.8%); and (4), malnutrition without comorbidities (n = 95, 27.8%). The risk ratios of mortality and predictors of survival were analyzed in the different groups.

Results: Of 342 patients, 186 (54.4%) patients had one or more comorbidities, and 156 (45.6%) patients had no comorbidities. Of 186 patients with comorbidities, 160 (86%) patients were malnourished, and only 26 (14%) had normal nutritional status. Of 156 patients without comorbidities, 95 (61%) were malnourished, and 61 (39%) had normal nutritional status. The relative risk of developing malnutrition in patients with comorbidities was significantly high, compared with patients without comorbidities (risk ratio, 3.9; 95% confidence interval [CI], 2.3 to 6.6; P = .001). According to time-dependent multivariate Cox regression analysis, the hazard ratio of mortality was 3.6 (95% CI, 1.1 to 11.7; P = .03) in patients with normal nutrition with comorbidities; 2.9 (95% CI, 1.1 to 7.8; P = .03) in patients with malnutrition without comorbidities; and 6.6 (95% CI, 2.6 to 16.5; P = .001) in patients with both malnutrition and comorbidities. The risk ratio of mortality in patients with both malnutrition and comorbidities was 3.7 times higher than in patients with malnutrition without comorbidities.

Conclusions: Patients with comorbidities are at high risk of developing malnutrition. Comorbidities and malnutrition, alone or together, constitute independent predictors of survival in these patients. Patients with both malnutrition and comorbidities demonstrate the worst survival. Malnutrition and comorbidities seem to exert a confounding effect on the survival of CAPD patients.