Depression as a predictor of mortality after heart attack

Investigators:
Dr Alan Goble, Dr Marian Worcester, Dr Barbara Murphy, Dr Peter Elliott, Heart Research Centre; Professor Erika Froelicher, University of California; Professor David Hare, Austin Hospital.

We recently completed a 25 year follow-up of men who had a heart attack during the early 1980s. The aim of this project, partially funded by beyondblue, was to investigate the impact of depression after a cardiac event upon long-term survival.

Effect of depression

Up to 15-20% of patients experience major depression after a heart attack.  Milder depressive symptoms, similar to a bereavement reaction, are even more common. Some, but not all, past studies have found that premature death is more common in depressed patients. However, it has been difficult to establish a causal link between depression and early death.

Original study

For the original study, information about patients was collected in hospital and at intervals during the first year via interviews, self-report questionnaires, clinical assessment and treadmill tests. Depression was assessed using the Beck Depression Inventory.

Tracking patients

Tracking patients after 25 years was a huge task. The Australian National Death Index was the primary source of information about the deaths of most patients. To locate patients not listed as dead, we consulted hospital records, as well as the cardiologists, cardiac surgeons and general practitioners who had previously treated these patients. For those patients or spouses not still living at their original addresses, an extensive search was made by post within Victoria and elsewhere to people listed in telephone directories with the same surname.

Results

We were able to determine the mortality status of 220 (98.4%) of the original 224 participants, a particularly impressive result. Fifty-six patients were still alive after 25 years. Of the non-survivors, most had succumbed to cardiovascular disease, with the remainder dying of other causes. Our study showed that depression was an important predictor of death up to 15 years. Interestingly, mild rather than severe depression appeared to predict earlier death. Our study confirmed previous findings showing that mortality is strongly related to older age and severity of the heart attack, indicated in our study by Killip class.

Further, we found that reduced functional capacity, determined by treadmill testing, showed a strong association with death over a 25 year period. In addition, anterior site of infarction, Norris Prognostic scores, a history of hypertension and resumption of smoking within four months were all markers of risk.   Interestingly, our study supported past research confirming that being able to confide in friends or partners is apparently a positive protective factor.

Importance of the study

This project has considerable significance for several reasons. The length of follow-up to 25 years is longer than previously reported. The baseline data originally collected was comprehensive, enabling analysis of psychosocial as well as physical and clinical predictors of death to be undertaken. 

Implications of the findings

Because depression was associated with earlier deaths in the first 10 years, prompt identification of depressed patients is important so that they can be appropriately managed. There is much evidence to show that depression is also strongly associated with other adverse outcomes, including poorer quality of life and non-adherence with advice.

Mr Con Lenihan

Con Lenihan, a patient in the original study, pictured above, was delighted to be contacted by Dr Worcester after 25 years. He recalled how his recovery was hampered by severe depression and anxiety after his heart attack, becoming extremely irritable, self absorbed and withdrawn. He said: "By attending the group rehabilitation program, I rapidly improved.  The exercise helped, as well as the support from staff and other patients". Although he was not able to resume work, Con became a model patient, losing weight, exercising regularly and quitting smoking for good. He now enjoys a good quality of life in a retirement hostel, supported by his four sons.

Funding: Beyondblue and The Eirene Lucas Foundation