Impact of depression on quality of life assessment in heart failure.

BACKGROUND: Depression is highly prevalent in patients with chronic heart failure (CHF) and may bias patients' reports of their health-related quality of life (HRQoL). Depressed patients may rate their limitations of HRQoL worse even when their condition is rather good. We aimed to examine whether co-morbid depression alters the relationship between disease severity and HRQoL, thus compromising the validity of a CHF-specific HRQoL measure.
METHODS: A sample of 233 outpatients with CHF (mean age 64.5 years, 70% male) was evaluated. Depression was measured with the Patient Health Questionnaire and CHF-specific HRQoL with the Kansas City Cardiomyopathy Questionnaire (KCCQ). CHF severity was assessed with physician ratings of the New York Heart Association (NYHA) functional class.
RESULTS: Both NYHA functional class and depression independently impacted the various subscales of the KCCQ. Regarding the symptom- and function-related subscales, a dose-response relationship between disease severity and HRQoL was observed also in depressed patients. In contrast, in the quality of life subscale covering life satisfaction an interaction effect of disease severity and depression was found. In this subscale, a dose-response relationship between increasing disease severity and worsening HRQoL was no longer present among the depressed.
CONCLUSIONS: Both disease severity and depression impacted each heart failure-specific HRQoL dimension while the presence of depression seemed to distort the relationship between disease severity and HRQoL in the quality of life subscale. As quality of life may depend more on the presence of depression than on the severity of CHF, assessing depression may help interpreting HRQoL scores. Copyright (c) 2008 Elsevier Ireland Ltd. All rights reserved.