Depression may increase exacerbations and hospitalizations for chronic obstructive pulmonary disease
It is well known that patients with chronic obstructive
pulmonary disease (COPD) frequently suffer from depression and anxiety, but according
to new research, depression and anxiety may actually cause increased hospitalizations
and exacerbations.
"This is an important and revealing finding, indicating
that for COPD patients, depression and anxiety must be treated as potential clinically
important risk factors, rather than simple comorbidities that are caused by COPD,"
said principle investigator of the paper, Jean Bourbeau, M.D., director of the
Respiratory Epidemiology and Clinical Research Unit of McGill University, in Montreal.
The research, published in the first issue for November
of the American Thoracic Society's clinical research journal, the American Journal
of Respiratory and Critical Care Medicine, is the first study to indicate a causal
relationship between depression and exacerbations and hospitalizations for COPD.
To determine whether depression and anxiety were independent
risk factors for COPD exacerbations and hospitalizations, the researchers prospectively
recruited nearly 500 patients with stable COPD from ten hospitals in Beijing.
Each patient was assessed at baseline for anxiety and depression as well as disease
severity. They were contacted monthly by telephone for one year to determine whether
they had experienced any exacerbations or hospitalizations.
"Almost a quarter of the patients we monitored were suspected
of having depression at baseline (13.8 percent possible and 9 percent probably
cases), and nearly one in ten were suspected of having anxiety (4.5 percent possible
and 5.1 percent probable cases)," said Dr. Bourbeau.
Depressed patients had a higher proportion of concurrent
anxiety than non-depressed patients. They also had higher mortality, more symptom-
and event-based exacerbations and hospitalizations and longer hospital stays than
non-depressed patients. They were also more likely to have had past exacerbations
and hospitalizations. Hospital stays were nearly two and a half times as long
for depressed patients, although the association did not reach statistical significance.
Anxiety was also associated with a greater risk of exacerbations
and longer hospital stays. Overall, among patients with anxiety who had at least
one exacerbation, the exacerbation lasted nearly twice as long as those without
anxiety, but there was no support for previous findings that hospitalizations
were affected by anxiety in length or frequency.
Because these effects were evident after adjustments
for all known confounding factors using a causal diagram, and because the outcomes
were measured after psychological exposures, the researchers assert that not only
is depression linked to greater risk of more and lengthier COPD exacerbations
and hospitalizations, but that their findings suggest a causal relationship.
"To our knowledge this is the first report of the possible
causal association between depressive symptoms and exacerbations and hospitalizations
in stable COPD. However, people have to realize that the causal relationship is
a complicated issue and will require further evaluation as part of other properly
designed longitudinal studies," wrote Dr. Bourbeau.
While they acknowledge that there may have been a differential
loss of depressed/non-depressed patients in follow up, because patients who withdrew
earlier had more severe COPD and were more depressed than those who completed
follow-up, it is likely that the association was underestimated than anything.
"Similarly, the association between anxiety and exacerbations may have been underestimated
due to the differential attrition," said Dr. Bourbeau.
The researchers proposed a number of possible explanations
for their findings?that depression itself may effect changes in the immune system;
that depression affects patients' ability to adapt to chronic symptoms, thereby
making them more likely to make frequent visits to the doctor and receive pharmacological
treatment; or depression may decrease self-confidence and increase feelings of
hopelessness, resulting in poorer self-care and poorer medication compliance.
"The results of this study can guide researchers and
clinicians to evaluate in COPD patients with depression the effectiveness of antidepressants
and psychotherapies on reducing exacerbations and related complications such as
hospital admissions," concluded Dr. Bourbeau.
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