Quality of life among patients with cardiac disease: the impact of comorbid depression

BACKGROUND: Patients with cardiac disease with or without depression may also have major physical and mental problems. This study assesses and compares the quality of life (QOL) of patients with cardiac disease with and without depression and accompanying comorbidities. METHODS: A cross-sectional study was conducted with a convenience sample of 388 patients with cardiac disease. The 12-item Short-Form (SF-12)-patient was used to measure physical component scale (PCS) and mental component scale (MCS) QOL, and the Patient Health Questionnaire (PHQ-9) was used to measure depression. The Charlson Comorbidity Index was used to estimate 10-year survival probability. Descriptive statistics, analysis of covariance (ANCOVA), chi-square tests, and binary logistic regression were used for analysis. RESULTS: The prevalence of minimal to mild depression was 65.7% [(95% CI (60.8, 70.4)] and that of moderate to severe depression was 34.3% [95% CI (29.6, 39.2)]. There was no significant association between the level of PHQ-categorised depression and age (p = 0.171), sex (p = 0.079), or ethnicity (p = 0.407). The overall mean PCS and MCS QOL was 32.5 [95% CI (24.4, 40.64)] and 45.4 [95% CI (44.4, 46.4)], respectively, with no significant correlation between PCS and MCS [r (Pearson’s) = 0.011; p = 0.830)]. There were QOL differences among the five PHQ categories (PCS: p = 0.028; MCS: p ≤ 0.001) with both MCS and PCS decreasing with increasing depression. ANCOVA (with number of comorbidities as the covariate) showed a significant age × ethnicity interaction for PCS (p = 0.044) and MCS (p = 0.039), respectively. Young Indo-Trinidadians had significantly lower PCS than did Afro-Trinidadians, while the converse was true for MCS. Depression, age, and number of comorbidities were predictors of PCS, while depression, age, and sex were predictors of MCS. CONCLUSIONS: Increasing severity of depression worsened both PCS and MCS QOL. Age and level of clinical depression predicted QOL, with number of comorbidities predicting only PCS and sex predicting only MCS. Efforts must be made to treat depression in all age groups of patients with cardiac disease.