High levels of neuroticism and low self-esteem are markers for vulnerability to depression, a condition associated with a higher risk of arrhythmias. The question as to whether these depression-related personality domains are related to cardiac repolarization (duration of QT interval) in apparently healthy men has been addressed in this study.
Methods
Participants were 658 clinically healthy males who underwent a health screening programme. QT interval duration was determined in the resting 12-lead electrocardiogram using an automated analysis program. Neuroticism was assessed by the short-scale Eysenck Personality Questionnaire and self-esteem by the Rosenberg self-esteem scale.
Results
Heart-rate corrected QT interval {QTc, formula of Bazett [Bazett HC. An analysis of time relations of electrocardiograms. Heart 1920;7:353–370]} progressively increased across quartiles of neuroticism ratings. By contrast, no differences in QTc were observed across different degrees of self-esteem. A multivariate regression analysis showed that neuroticism was a statistically significant, independent predictor of QTc duration.
Conclusion
After adjustment for potential confounders, neuroticism scores independently predicted QT interval duration in apparently healthy men. These findings highlight the possibility that higher arrhythmic risk could be present not only in patients with clinical depression but also in depression-prone, otherwise healthy individuals.
Ventricular repolarization is a complex electrical phenomenon, and as direct repolarization measurements obtained from epicardial monophasic action potential and body surface mapping have been found to be correlated with the QT interval on surface electrocardiograms (ECGs), simple measurements of the QT interval have been regarded as essential in monitoring cardiac repolarization [1] and [2].
During the past years, a bulk of published data has clearly shown that a prolonged QT interval is a risk marker for cardiovascular morbidity and mortality in numerous different populations, including initially healthy subjects [3], [4] and [5], subjects referred for Holter monitoring [6], as well as clinical cohorts of patients with diabetes mellitus [7] and [8] and cardiovascular disease [9] and [10]. Among the pathophysiological mechanisms advocated to account for this relationship, cardiac autonomic imbalance with decreased parasympathetic and increased sympathetic modulations has emerged as one of the most intriguing pathways [11].
Working from the assumption that an altered autonomic function may also be a feature of different psychiatric disorders, some authors have recently demonstrated significant alterations of the QT interval in clinical cohorts of psychiatric patients, including subjects with social phobia [12], panic disorder [13], and major depression [14]. The latter findings are of particular importance, because it is well-known that depressed patients show an increased risk for a number of cardiovascular complications, including ischemic heart disease [15], serious ventricular arrhythmias [16], and sudden cardiac death [17]. It has been therefore proposed that dysregulation of ventricular repolarization may be one of the mechanisms linking depressive mood states and cardiac risk [13], [14], [16] and [18]. At this time, however, no studies have assessed whether a relation exists between QT interval duration and personality-related vulnerability to depression. Nonetheless, this issue could be of interest in view of the strict interrelationships between the onset of major depressive episodes and personality traits in the domains of high neuroticism and low self-esteem [19].
Neuroticism is a dimensional measure of an individual's tendency to experience negative emotions that are manifested at one extreme as anxiety, low mood, and hostility and at the other as emotional stability [20]. Reflecting a tendency toward states of negative affect, it, together with extraversion and psychoticism, constituted the three key dimensions of personality, according to Eysenck and Eysenck [20], and has been included in nearly all theories of personality. Neuroticism is also known to possess good psychometric properties of item and construct validity, stability, and cross-cultural validation [21].
Differently from neuroticism, self-esteem has been given a number of different definitions, each emphasising different aspects [22]. The most significant division remains between the view that self-esteem is a generalised feeling about the self and the view that it is the sum of a set of judgments about one's value, worthiness, and competence in various domains [23]. In any case, different independent studies have clearly indicated that low self-esteem could be a marker for developing clinically relevant depressive episodes [24] and [25].
In the present report, we hypothesized that depression-related personality traits of neuroticism and self-esteem could be associated with QT interval duration as a possible pathway in the genesis of higher cardiovascular risk observed in depressive mood states. We addressed this issue by studying the relationships of neuroticism and self-esteem scores with QT interval in an Italian cohort of apparently healthy men undergoing a cardiovascular screening programme. We also reasoned that if these personality domains are independently related to QT interval duration, then effects should persist after statistical control for demographical, clinical, and biochemical characteristics of the study participants.
