Depression Doubles Risk Of Death After Bypass Surgery
DURHAM, N.C. – In the largest and longest study of its kind,
researchers at Duke University Medical Center have definitively
shown what previous studies have hinted at – depression is a
strong independent risk factor for death in patients who have
undergone coronary artery bypass surgery to restore blood flow
to the heart.
Because depression appears to double the chances of death,
the researchers believe that bypass surgery patients should be
screened to assess a patient's likelihood of depression.
The findings of the Duke team's study were published in the
August 23, 2003, issue of the journal Lancet. The study was
supported by numerous grants from the National Institutes of
In analyzing the medical records of more than 800 patients
who underwent bypass surgery at Duke, the researchers found
that those patients with moderate to severe depression at the
time of their surgery -- or those with mild depression prior to
surgery that persisted for at least six months following
surgery -- were more than twice as likely to die during the
follow-up period. Some patients were followed as long as 12
years after surgery, with the average follow-up being 5.2
"Despite our advances in surgical and medical management of
patients after coronary artery bypass surgery, depression is an
important independent predictor of death after surgery and
should be carefully monitored and treated if necessary," said
clinical psychologist James Blumenthal, Ph.D., lead author on
the Lancet article. "We believe that psychological assessment
before and after surgery could be a low-cost and relatively
easy way of potentially saving lives."
Because bypass surgery, which has been performed for more
than 30 years, has been so successful in saving lives, past
studies with small samples have had so few deaths that it has
been difficult for researchers to make statistically
significance conclusions. However, the Duke researchers have
been collecting clinical and psychological data on heart
surgery patients for more than two decades, which allows them
to perform these long-term outcomes studies.
"We were very surprised at the strength of the association
between depression and mortality," said Mark Newman, M.D.,
chairman of anesthesiology at Duke and co-investigator of the
study. "As we statistically controlled for other risk factors,
we began to worry that the association might be due to the
advanced age and other illnesses, which could be a reason for
"But, after all the statistical analyses, we found that
depression is truly separate from every other risk factor as a
robust and significant independent risk factor," Newman said.
"The key for us now is to determine whether or not treating the
depression – whether by medications, psychological approaches
or exercise – can positively affect outcomes."
The Duke team analyzed the records of 817 patients
undergoing bypass surgery from 1989 to 2001. During that time
period, 122 patients, or 15 percent, died. Patients who were
already being treated for depression or other mental illnesses
were excluded from the analysis.
All of the patients took a standardized test to assess
symptoms of depression the day before surgery as well as 6
months after surgery. The test is known as the Center for
Epidemiological Studies – Depression (CES-D) survey, a
20-question self-report instrument that can be administered by
psychologists in less than 15 minutes.
"Of that group of patients, thirty-eight percent met the
criteria for being depressed," Blumenthal said. "Specifically,
twenty-six percent we considered to be mildly depressed, and
and additional twelve percent with moderate to severe
Patients who scored below 16 on the CES-D were considered
non-depressed, with a score between 16 and 26 being considered
mildly depressed. Patients scoring above 27 were considered
moderate to severely depressed. The researchers then examined
the relationship of the depression scores with the subsequent
During the 12-year follow-up period, 10 percent of the
patients who were never depressed died, compared to 19 percent
of patients who were persistently depressed, the researchers
"Interestingly, patients with mild depression – a score
between 16 and 26 – before surgery and who had scores that
remained high six months later had the same risks as those with
moderate to severe depression before surgery," Blumenthal
explained. "However, those mildly depressed patients whose
scores decreased after six months were at no more risk than
those who weren't depressed to begin with."
The researchers point out that, while their study
demonstrated a strong association between depression and
mortality, it could not determine the mechanisms involved.
Although there a many theories, further studies that pinpoint
the mechanism will be important to developing a successful
intervention, they said.
Depression has been linked to other such cardiovascular risk
factors as insulin resistance, hypertension, obesity, increased
cigarette smoking, alcohol abuse and physical inactivity. The
Duke researchers are currently investigating several potential
mechanisms, including the effects of depression on platelet
aggregation and heart rate variability.
"The overall goal of all our efforts is to improve the
quality and quantity of life for patients undergoing bypass
surgery," Newman said. "This study is just one part of progress
toward achieving that goal."
Other members of the Duke team included Heather Lett,
Michael Babyak, Ph.D., William White, Peter Smith, M.D., Daniel
Mark, M.D., Robert Jones, M.D., and Joseph Mathew, M.D.