Mood state as a predictor of neuropsychological deficits following cardiac surgery

Abstract

Objectives: mood disorders and neuropsychological deficits are both commonly reported occurrences after cardiac surgery. We examined the relationship between mood state and postoperative cognitive deficits in this population.Methods: assessments of neuropsychological functions and mood state (depression, anxiety, stress scales; DASS) were performed preoperatively and postoperatively on 147 patients undergoing cardiac surgery.Results: the incidence of preoperative depression, anxiety, and stress symptomatology was 16%, 27%, and 16%, respectively. The incidence of postoperative anxiety symptomatology significantly increased to 45% (p<0.001), while the incidence of depression and stress symptomatology remained stable (19% and 15%, respectively; ns). Changes in mood state did not influence changes in neuropsychological performance. Preoperative mood was a strong predictor of postoperative mood, and was related to postoperative deficits on measures of attention and memory.Conclusions: an assessment of preoperative mood is critical in identifying patients at risk of postoperative mood disorders and neuropsychological deficits. Measures assessing somatic manifestations of anxiety may not be suitable for a surgical population.

Introduction

High rates of depression and anxiety are commonly reported prior to and following cardiac surgery [1]. McKhann et al. [2] reported 27% of their sample of coronary artery bypass graft (CABG) patients had a clinically elevated score on the Center for Epidemiological Study of Depression (CES-D) scale prior to surgery. Langeluddecke et al. [3] using the same scale reported the incidence of preoperative depression in their sample of CABG patients was 36%, while 30% had clinically elevated scores on the Spielberger State Anxiety Inventory.

For most patients, preoperative mood states persist after cardiac surgery and in fact, preoperative mood state is consistently reported to be a major contributor to the prediction of postoperative depressive and anxiety symptoms [2], [4], [5]. Magni et al. [4] reported preoperative depression scores accounted for 34% of the variation in postoperative depressed mood, while preoperative psychological distress accounted for 29% of the variation in postoperative anxiety levels. More than 50% of the patients with preoperative depression in the McKhann study [2] were depressed 1 month after surgery, compared with 13% of patients not depressed prior to surgery.

Postoperative neuropsychological deficits are a common complication of cardiac surgery and the incidence of these deficits has been shown to range from 25% to 80% [6]. It is well recognised that emotional states such as depression and anxiety can produce decrements in neuropsychological test performance [7], with the cognitive domains of attention and memory appearing to be particularly susceptible to the effects of mood. It is a common perception that mood disorders may contribute to the reporting of neuropsychological deficits following cardiac surgery, and thus, researchers have been cautioned to include measures of mood states in their test batteries, and to control for mood state when assessing postoperative cognitive deficits [8]. Despite this, there has been limited research assessing the relationship between mood state and cognitive deficits in a cardiac surgical population.

In a recent study by McKhann et al. [2], the relationship between depression and postoperative cognitive deficits was investigated in a cohort of 127 CABG patients. They demonstrated no correlation between preoperative depression and preoperative neuropsychological test performance, and similarly, no correlation between postoperative depression and postoperative neuropsychological scores. Furthermore, they reported minimal correlations between changes in depression and neuropsychological performance. However, this study failed to analyse the potentially critical relationship between preoperative depression and postoperative neuropsychological deficits.

Although depression and anxiety are regarded as conceptually distinct, attempts to quantify these constructs using both self-report measures and clinical ratings have often demonstrated a high degree of overlap between the two conditions. Existing measures of anxiety and depression, such as the Hamilton scales for anxiety and depression have been shown to intercorrelate highly [9], [10], while anxiety measures such as the Beck anxiety inventory (BAI) fail to discriminate between symptoms of physical arousal and symptoms of generalised anxiety (e.g. tension or agitation) [11].

In a research program spanning from 1979 to 1990, Lovibond and Lovibond [12], [13] attempted to develop self-report measures of depression and anxiety that would cover the full range of core symptoms of these conditions while providing maximum discrimination between the constructs. During development of the scales, another factor emerged from non-discriminating depression and anxiety items. The resultant factor consisted of items addressing tension and irritability and was thus labelled “stress”. Several factor analytical studies on clinical [14], [15] and non-clinical samples [12], [13] have confirmed the three-factor structure of the depression, anxiety, stress scales (DASS). The depression scale consists of items that measure symptoms typically associated with dysphoria and anhedonia (e.g. sadness, lack of interest). The anxiety scale is similar to the BAI and includes items that are related to symptoms of physical arousal and panic attacks (e.g. trembling, faintness). The stress scale includes items assessing symptoms of tension, irritability, and a tendency to overact to stressful situations.

Studies examining the psychometric properties of the DASS have provided strong evidence for the internal consistency and temporal stability of the scales [12], [13], [14], [15], [16], and have demonstrated that the DASS provides better discriminant validity relative to other existing measures of depression and anxiety [12]. The DASS therefore has the advantage of distinguishing between the three domains of depression, anxiety, and stress in a brief and psychometrically sound manner. However, although the DASS has been validated on a sample of myocardial infarction patients [13], it is yet to be applied to the cardiac surgery population.

The aim of this study is to apply the DASS to examine the incidence of depression, anxiety, and stress preoperatively, and in the immediate postoperative period, and to determine the influence of mood state on postoperative neuropsychological dysfunction in a sample of cardiac surgery patients.