December 2, 2011 — Major depressive disorder (MDD) may lead to cardiovascular disease (CVD) in older adults, new research suggests.
In secondary analysis of the Mechanisms and Outcomes of Silent Myocardial Ischemia (MOSMI) study, which included almost 900 participants with a mean age of 60 years, those with MDD showed a significantly slower short-term heart rate recovery time after exercising than their nondepressed counterparts.
According to the investigators, this delayed ability to return to a normal heart rate can be a powerful tool for predicting CV events and mortality.
"The delayed rate indicates a dysfunctional biological stress system, or a dysfunctional 'flight or fight response,' and we believe this can contribute to an increased risk for heart disease," senior author Simon Bacon, PhD, codirector of the Montreal Behavioral Medicine Center and associate professor in the Department of Exercise Science at Concordia University, Montreal, Quebec, Canada, told Medscape Medical News.
The researchers note that the study's results reinforce findings from previous research suggesting that those who suffer from MDD should be tested for CVD.
"Both of these health issues should be treated to minimize risk of severe consequences," said Dr. Bacon.
The study was published in the November issue of Psychophysiology.
Dysfunctional Fight or Flight Response
According to the investigators, previous studies suggest that individuals suffering from depression may be twice as likely to suffer a heart attack as those who are not depressed.
In addition, a recent study reported on by Medscape Medical News found that depression and previous suicide attempts were significant predictors of heart disease mortality in young adults.
"There have been 2 competing theories as to why depression is linked to CVD," said lead author Jennifer Gordon, PhD candidate from the Psychology Department at McGill University in Montreal, in a release.
"Depressed people may have poorer health behaviors, which in turn lead to heart problems. The other possibility is physiological: a problem with the fight or flight response."
In other words, it may be that people with depression have an autonomic nervous system (ANS) imbalance. The investigators note that heart rate variability is often used as a measure of ANS dysfunction.
"Our study is the first to examine the role of a dysfunctional fight or flight response in depression in a large population," said Dr. Gordon.
The MOSMI trial was created to examine risk factors for silent ischemia and its effect on CV outcomes. For this analysis, the investigators evaluated data on 886 MOSMI participants (68.8% men; mean age, 60 years) who underwent a 2-day exercise stress test using a treadmill and a single photon emission computed tomography imaging protocol.
While at rest, at peak exercise point, and at 1 and 5 minutes postexercise, the participants had their heart rate and systolic and diastolic blood pressures measured.
The Primary Care Evaluation of Mental Disorders and Beck Depression Inventory II (BDI-II) were also administered to all patients, along with a questionnaire on sociodemographic data and medical history, including depressive symptoms and medication usage.
Slower Heart Rate Recovery
Overall, 5.8% of the participants were found to have MDD. These patients had a significantly slower heart rate recovery time at the 1-minute postexercise checkpoint compared with those who were not depressed (adjusted difference, 3.7 beats per minute; P = .026).
However, there were no significant differences between the 2 groups in heart rate recovery time at the 5-minute postexercise checkpoint.
"The classic fight or flight response is very adaptive over time. This means the system is easily activated but can also quickly shut itself off after a stress is removed. So it wasn't surprising to see that the depressed patients' heart rates were still quite elevated at the earlier mark, and not at the later mark," Dr. Bacon said.
There were no significant between-group differences in either systolic or diastolic blood pressure recovery at either time.
In addition, BDI-II scores were found to not be predictive of CV recovery, suggesting that "subclinical levels of depression are not as reliably associated with ANS dysfunction," write the researchers.
"This may explain some of the variance in previous studies examining the relation between depression and exercise recovery."
Dr. Bacon said that overall, he would recommend that mental health clinicians who see patients with MDD should think about how the disorder affects other physical elements, and that cardiologists should consider asking about the mental health status in their heart patients.
"The key element here is to make sure these different disciplines have a little more awareness of what's happening with the patient. Ultimately, what we want to do is make people's lives better."
"There's been a long-term interest in whether the autonomic dysregulation that people have found with depression could be the cause of both the development of heart disease and a worse prognosis in those with comorbid depression and heart disease," Wayne Katon, MD, professor and vice chair in the Department of Psychiatry and Behavioral Sciences at the University of Washington Medical School in Seattle, told Medscape Medical News.
"This study is better than some of the other past studies because it measured major depression (not just depressive symptoms) and both long- and short-term return to normal heart rate. And they controlled for exercise capacity," said Dr. Katon, who was not involved with this research.
He noted that most people with MDD have less exercise capacity, probably because the disorder is associated with an increased sedentary lifestyle.
"Many people with depression have inadequate treadmill tests. But this study used a type of test that was set up for people who were older and more sedentary. So they probably didn't have to deal so much with people giving up and quitting before a good read could be recorded," said Dr. Katon.
"Of course the study findings will need to be replicated, but it does suggest that depression is associated with at least short-term decreased ability of the heart to return to a normal rate."
The main takeaway of this study, said Dr. Katon, is that patients with CVD should be screened for depression.
"We routinely screen for diabetes and other medical conditions because they worsen prognosis. Because there's excellent evidence that depression also worsens prognosis, we should be screening for it," he said.
"We're also finding a bidirectionality between depression and chronic medical illness. So certainly screening our aging population for depression in general is important. And treating it better is essential."
The study was supported by grants from the Heart and Stroke Foundation of Quebec and the Canadian Institutes of Health Research, and from the Canadian Hypertension Society and le Fonds de la recherche en santé du Quebec. The study authors and Dr. Katon have disclosed no relevant financial relationships.
Psychophysiology. 2011;48:1605-1610. Abstract
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Cite this: Major Depression Linked to Heart Disease in Older Adults - Medscape - Dec 02, 2011.