"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
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
"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
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
"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.