Poor Sleep Quality is Associated with Depressive Symptoms in Patients with Heart Disease

Depression in cardiac patients has gained importance due to increased mortality. Although sleep disturbances are a core symptom
of depression, the prevalence and patterns of sleep disturbances in heart disease have hardly been examined regarding depression.

This cross-sectional study aims to examine sleep disturbances and depressive symptoms in consecutively admitted cardiac patients
and depressed patients.

Two hundred four inpatients (113 male, 91 female) were examined: 94 cardiac inpatients (mean age 49.3 ± 14.3 years) with different
heart diseases and 110 psychiatric inpatients (mean age 41.6 ± 13.0 years) with depressive disorders (DP). A depressive episode
according to International Classification of Diseases (ICD)-10 was also diagnosed in 14 of the cardiac patients (DCP). The
Pittsburgh Sleep Quality Index (PSQI) and the Beck Depression Inventory (BDI) were used to assess subjective sleep quality
and severity of depressive symptoms.

Poor sleep quality (PSQI > 5) was reported in all comorbid DCP (PSQI 12.00 ± 3.53, BDI 17.86 ± 4.28), in 60% of the 80 non-DCP
(PSQI 5.59 ± 3.73, BDI 4.47 ± 3.07), and in 86.4% of the DP (PSQI 11.76 ± 4.77, BDI 27.11 ± 10.54). The cardiac inpatients
showed a significant correlation between increased depressive symptoms and the PSQI components subjective sleep quality (r = 0.40) and daytime dysfunction (r = 0.34). Both sleep components were significant predictors of self-rated depression (R² = 0.404).

Most cardiac patients experience poor sleep quality. Self-reported sleep disturbances in heart disease could serve as predictors
of clinical or subclinical comorbid depression outside of a psychiatric setting in cardiology and other fields, and such patients
should be referred to consultation-liaison psychiatry or polysomnography where sleep disorders like sleep apnea are suspected.