Depression and delirium in cardiac surgery patients

Abstract

Depression is common in persons with cardiac disease, and there is a well-known association between depression and increased cardiovascular morbidity and mortality. Preoperative depression has been associated with postoperative delirium (POD) after general surgery but the association between depression and POD in persons undergoing cardiac surgery is sparsely studied. Postoperative delirium affects a large proportion of patients undergoing cardiac surgery. Delirium phenotypes are commonly divided into hyper- and hypoactive, where hypoactive symptoms (reduced motor activity and withdrawal) often are overlooked due to their discreet character. To our knowledge, there are no studies describing patients’ experiences of hypoactive delirium after cardiac surgery. Although the association between depression and mortality after coronary artery bypass grafting has been confirmed, the association between preoperative depression and long-term survival after cardiac surgery is sparsely studied.

The overall aim of this thesis was to contribute to the understanding of the association between depression and delirium, as well as depression and mortality in patients undergoing cardiac surgery.

Study I was a systematic literature review and meta-analysis including cohort studies reporting odds ratios (ORs) and 95% confidence intervals (CIs) for POD after cardiac surgery in patients with preoperative depression compared to patients without depression. ORs and 95% CIs for POD were calculated using random-effects models. Seven studies were included with a combined study population of 2066 patients. The pooled prevalence of POD was 26% and preoperative depression was present in 9% of the total study population. All studies showed a positive association between preoperative depression and POD. Patients with depression had a pooled OR of 2.31 (95% CI 1.37–3.90) for POD.

Study II was a population-based cohort study including 1120 persons undergoing cardiac surgery from 2013–2016. Preoperative depression was defined by the Patient Health Questionnaire-9, and baseline characteristics were contained in the Swedish Cardiac Surgery Registry. POD was evaluated by assessing medical records. The association between preoperative depression and POD was determined through multivariable logistic regression analysis. A total of 162 patients (14,5%) reported depressive symptoms preoperatively. The incidence of POD was 26%. The overall adjusted odds of delirium were 2.19 times higher in patients with depressive symptoms compared to controls (95% CI 1.43–3.34).

Study III was a qualitative descriptive semi-structured interview study aiming to describe cardiac surgery patients' experiences of hypoactive delirium. Twelve cardiac surgery patients with hypoactive symptoms of delirium were purposefully selected. The data were analyzed by qualitative content analysis with an inductive, latent approach. Two themes based on eight sub-themes emerged: “Dream or reality in parallel worlds” included disturbing experiences of existing in parallel realities with cognitive effects, residual nightmares, and illusions that occasionally persisted after hospital discharge. “Managing the state of hypoactive delirium” included experiences of intellectually dealing with hypoactive delirium with assumptions of causes and cures, and through interactions like communicating with others. The delirium experienced by the participants was considerably more extensive than what had been documented in their medical journals, an indication that hypoactive delirium is overlooked.

Study IV was a population-based cohort study investigating the same study cohort as in Study II. The vital status at end of the study was collected from the Swedish Cardiac Surgery Registry on December 15, 2022. During a mean follow-up of 7.2 years (maximum 9.2 years), there were 36 deaths in 1129 person-years (PYs) in the depressed group, compared to 160 deaths in 6889 PYs in the non-depressed group. In the adjusted analysis, self-reported depressive symptoms were associated with worse long-term survival (HR=1.66; 95% CI, 1.09-2.54) compared with no reported depressive symptoms. The absolute survival differences (% and 95% CI) between the non-depressed and the depressed patients were -1.9 (-3.9–0.19), -5.7 (-11– -0.01), and -9.7 (-19– -0.4) after one, five, and eight years, respectively.

In conclusion, depression is a significant, independent risk factor for POD and worse longterm survival after cardiac surgery. Depression screening is important to identify patients at risk, and delirium assessment tools should be used to detect all kinds of POD.