Influence of Co-Morbidity on Health-Related Quality of Life in Patients Treated with Hemodialysis

Abstract

Studies on the outcome of hemodialysis (HD) patients over time have mainly focused on morbidity and mortality, but currently, the importance of measuring the patient's health-related quality of life (HRQoL) is being increasingly recognized. On the other hand, comorbidity is the single most important determinant of outcome in patients on HD. The aims of this study were to evaluate HRQoL in patients at the initiation of HD therapy (incident cohort), and in patients on long-term HD treatment (prevalent cohort), and to establish the relationship between the presence of comorbidity and patient's HRQoL. The study enrolled 229 patients on HD, divided into two groups: prevalent cohort comprised 192 patients on chronic HD more than 3 months, and incident cohort with 37 patients who started their dialysis during the study. Comorbidity was assessed using the Index of Coexistent Diseases (ICED), including two sub-indexes: Index of Disease Severity (IDS), a medical record review of 16 medical conditions, and Index of Physical Impairment (IPI), an observer-based assessment of 11 physical functions. ICED scores range from 0 to 3, with higher levels reflecting more severe comorbidity. Patient's self-assessment of HRQoL was measured by the 36-item Short Form Health Survey Questionnaire (SF-36), encompassing 8 summary scales and 2 summary dimensions. Based on the ICED index level, in both groups of patients (prevalent and incident group), a high presence of associated diseases was observed, i.e. 56.8 % and 67.6 % respectively. Indicators of comorbidities have negative and statistically significant correlation, so that any increase of IDS and IPI indexes produces significant decrease of HRQoL parameters. HRQoL summary scales in both groups of patients were similar, but generally with lower values in incident subjects and with statistical significance only in social functioning (SF) scale (40.5 +/- 24.9 vs 51.0 +/- 27.2). In the incident group of patients, one year of HD treatment was associated with a slight improvement in all HRQoL parameters, but statistical significance (p < 0.05) was observed only in the role-physical limitation (RP) scale and SF scale. In the patients on HD treatment, comorbid conditions have negative and statistically significant correlation with parameters of HRQoL, and could explain poor HRQoL to a remarkable extent. One year after starting HD, patients reported better scores in some domains, especially in the RP and SF scale. From a clinical perspective, parameters of HRQoL and comorbidities should be considered in the follow up of patients treated with HD.