Impact of depression on the quality of sleep and immune functions in patients with coronary artery disease

Background The risk of major depressive disorder (MDD) and insomnia is higher in patients with coronary heart disease (CHD) than in the general population. In addition, immune inflammation may be a shared aetiological factor for mental disorders and CHD. However, it is unclear whether MDD is associated with poor sleep quality and cell-mediated immune function in patients with CHD. Aims This study investigated the impact of depression on sleep quality and cell-mediated immune functions in patients with CHD and examined discriminative factors in patients with CHD with and without MDD. Methods This cross-sectional retrospective study was conducted at the Zhejiang University School of Medicine affiliated with Sir Run Run Shaw Hospital. The study population consisted of 84 patients with CHD assigned to two groups based on their Hamilton Depression Rating Scale (HAMD) score (CHD with MDD (HAMD score of ≥10) vs without MDD). Subjective sleep quality, systemic inflammatory response and cell-mediated immune functions were assessed in patients with CHD with (n=50) and without (n=34) MDD using the Pittsburgh Sleep Quality Index (PSQI), routine blood tests and flow cytometry. The relationships between variables were ascertained using Pearson’s product–moment, and linear discriminant analysis was used to explore the discriminative factors between groups. Results Patients with CHD with MDD had significantly poorer sleep quality than those without MDD (Z=−6.864, p<0.001). The Systemic Inflammation Index (SII) and CD4+/CD8+ T-cell ratios were higher in patients with CHD with MDD than in those without MDD (Z=−3.249, p=0.001). Patients with CHD with MDD had fewer CD3+CD8+ and CD3+ T cells (Z=3.422, p=0.001) than those without MDD (t=2.032, p=0.045). Furthermore, patients with CHD with MDD may be differentiated from those without MDD using the PSQI, SII and T-cell levels, as these variables correctly classified the depressed and non-depressed groups with an accuracy of 96.4%. Conclusions MDD may be responsible for poor sleep quality, increased cell-mediated immunity and SII in patients with CHD, which are discriminative factors for CHD in the depressive state. Clinicians should be aware of these interactions, as treatment for depressive symptoms may also improve CHD prognosis.