Depression and risk of sudden cardiac death after acute myocardial infarction: testing for the confounding effects of fatigue.

OBJECTIVES: This study examined the impact of depressive symptoms and social support on 2-year sudden cardiac death (SCD) risk, controlling for fatigue symptoms.

METHODS: Myocardial infarction (MI) patients (N = 671) participating in the Canadian Amiodarone Myocardial Infarction Arrhythmia Trial completed measures of depression, hostility, and social support.

RESULTS: After controlling for significant biological predictors, psychosocial predictors of increased SCD risk in the survival analysis were greater social network contacts (RR = 1.04; 95% CI = 1.01-1.06; p < .007), lower social participation (RR = 0.98; 95% CI = 0.96-1.00; p < .05), and, in placebo-treated patients, elevated depressive symptoms (RR = 2.45; 95% CI = 1.14-5.35; p < .02). Fatigue was associated with SCD (RR = 1.31; 95% CI = 1.11-1.53; p < .001), and, when included in the model, diminished the influence of depression (RR = 1.73; 95% CI = 0.75-3.98; p = .20). When the cognitive-affective depressive symptoms were examined separately from somatic symptoms, there was a trend for an association between cognitive-affective symptoms and SCD in placebo-treated patients after controlling for fatigue (RR = 1.09; 95% CI = 0.99-1.19, p < .06).

CONCLUSIONS: Symptoms of depression and fatigue overlap in patients with MI. The trend for the cognitive-affective symptoms of depression to be associated with SCD risk, even after controlling for dyspnea/fatigue, suggests that the association between depression and mortality after AMI cannot be entirely explained as a confound of cardiac-related fatigue. The independent contribution of social participation suggests a role of both depressive symptomatology and social factors in influencing mortality risk after MI.