Depression and five year survival following acute myocardial infarction: A prospective study

Abstract

Depression has been shown to be a risk factor for mortality during the 12 months following an acute myocardial infarction (MI), but few studies have examined whether it is associated with increased risk over longer periods. Most of the existing studies utilized depression questionnaires rather than diagnostic interviews, the gold standard for clinical depression diagnosis. The purpose of this study was to determine whether interview-diagnosed clinical depression affects survival for at least 5 years after an acute MI.

Vital status was determined for 163 patients with major depression, 195 with minor depression or dysthymia, and 408 nondepressed patients, during a median follow-up period of 60 months after an acute MI. Survival analysis was used to model time from the index MI to death.

There were 106 deaths during the follow-up. After adjusting for other risk factors for mortality, patients with either major or minor depression (HR = 1.76; 95% CI: 1.19 to 2.60), major depression alone (HR = 1.87; 95% CI: 1.17 to 2.98), or minor depression alone (HR = 1.67; 95% CI: 1.06 to 2.64) were at higher risk for all-cause mortality compared to the nondepressed patients.

Depression is an independent risk factor for death 5 years after an acute MI. Even minor depression is associated with an increased risk. Although it is not known whether treating depression can improve survival, patients with depression should be recognized as being at increased risk long after their acute MI.

Introduction

Depression is a risk factor for mortality following an acute myocardial infarction (MI) (Barth et al., 2004, Carney and Freedland, 2003, Glassman and Shapiro, 1998, van Melle et al., 2004). Most studies of depression and mortality after MI have followed patients for 12 months or less after the acute event. However, clinical depression is often chronic or recurrent. Therefore, the adverse effects of depression might continue for months or even years after an MI.

A few studies have included longer follow-ups of depressed post-MI patients. However, most of these have used self-report inventories to assess depression (Grace et al., 2005, Lane et al., 2002, Strik et al., 2003, Lesperance et al., 2002), and they have provided mixed support for a long term adverse effect of depression on mortality. For example, using the Beck Depression Inventory (BDI)(Beck et al., 1979), Lespérance and his colleagues found a significant dose–response relationship between BDI scores in the days following the MI and mortality over a five year period (Lesperance et al., 2002). Lane et al., on the other hand, found no relationship between BDI scores following an acute MI and three year mortality (Lane et al., 2002), although they also reported no relationship after one year in the same cohort (Lane et al., 2001). One of the problems in defining depression by self-report questionnaires like the BDI is that they are not highly specific for clinical depression (Strik et al., 2001). Thus, an elevated score may reflect transient sadness, anxiety, other psychiatric disorders, general distress secondary to a life-threatening experience, or even the symptoms of the medical illness.

The gold standard for defining clinical depression is a diagnostic interview. However, only a few interview-based studies have examined the relationship between depression and long term survival following an acute MI. Dickens and colleagues did not find a significant relationship between depression prior to an acute event and 8 year mortality, using either the Hospital Anxiety and Depression Survey (HADS) self-report inventory, or a diagnostic interview that was administered to a subset of these patients (Dickens et al., 2007). However, they identified patients who were depressed prior to rather than immediately following the acute MI, in contrast to previous investigations. On the other hand, Drago and colleagues found that an interview-based diagnosis of depression following an acute MI predicted 5-year mortality, but this was a small study with only 15 patients who met criteria for major depression (Drago et al., 2007). Furthermore, it did not address the question of whether minor depression also poses a risk.

We previously reported the results of a two year median follow-up of a cohort of 358 post-MI patients with an interview-based diagnosis of either major or minor depression, and 403 nondepressed patients (Carney et al., 2003). This paper reports the results of a 5-year follow-up of this cohort.