http://well.blogs.nytimes.com/2011/12/01/depression-may-slow-exercise-recovery/?ref=healthExercise is known to ease the symptoms of depression. But does depression change the way the body responds to exercise?
A new study suggests that clinical depression may hamper the body’s ability to recover from physical activity, prolonging the amount of time it takes for a depressed person’s heart rate to slow down and return to normal after a workout. Although it may sound minor, some research suggests that a difference of even just a few beats a minute during post-exercise recovery is associated with a shorter life span.
Scientists say the findings may help shed light on the well-known link between depression and heart disease. Studies show that depressed people have an increased risk of heart attacks, and heart patients who develop depression die sooner than heart patients without depression.
The new study, published in the November issue of the journal Psychophysiology, included 886 healthy adults, including 51 with a diagnosis of major depression. All of the subjects were given stress tests on a treadmill, and their blood pressure and heart rates were measured both at rest and during the exercise test, as well as at one-minute and five-minute intervals afterward.
Over all, compared with the subjects without depression, it took significantly longer for the depressed subjects’ heart rates to slow down to normal after the stress test. The difference was about 3.7 beats a minute.
That seemingly small disparity may have a major effect on mortality, other research suggests. A study at Stanford of more than 2,000 men who underwent similar stress tests throughout a seven-year period, for example, found that men who died during the followup period had all taken slightly longer to recover after exercise during the study. On average, these men had returned to their normal heart rates about three beats a minute more slowly than the other men in the study, which was published in 2001.
“That really highlights how important this kind of physiological disruption can be,” said Simon Bacon, an associate professor of exercise science at Concordia University in Montreal and senior author of the new paper.
While the cause of the heart-rate disparity in the depressed subjects is unclear, Dr. Bacon and his colleagues speculated that people with major depression have a dysfunctional stress response. Normally, in response to a threat or stressful event, a person’s nervous system ramps up as the heart rate accelerates, pupils dilate and adrenaline flows. But when the stress is removed, this state of high alert should diminish.
“The system is supposed to come back to normal quite quickly,” Dr. Bacon said. “But what we’re seeing in the patients with depression is the system is not relaxing and coming back to normal as it should. Something about being depressed probably has some influence on the circuitry of the brain that causes the stress response to become dysfunctional.”
Most research into depression and exercise has focused on the benefits of physical activity for easing the symptoms of anxiety, depression and other mood disorders. Dr. Bacon said patients with depression should not be discouraged from physical activity, and should continue to look at exercise as a form of treatment. He pointed out that his study used an unusually “acute” exercise test to stress the subjects.
“This does not suggest a single bout of exercise is harmful,” he said.
In fact, he added, regular exercise may even improve heart-rate recovery in people with depression. As for the next step, Dr. Bacon said future studies would look at whether cognitive behavioral therapy or certain drugs might be able to improve the stress response. At the same time, imaging studies might help pinpoint the underlying problem in the brain’s circuitry.